…oftDelete

* DeleteQueryBuilder, UpdateQueryBuilder and SoftDeleteQueryBuilder abstracted to ModificationQueryBuilder
* SoftDeleteQueryBuilder extends UpdateQueryBuilder

…er events

* All transaction code abstracted back to QueryBuilder.execute(), new abstract method executeInsideTransaction() added
* All before/after events abstracted back to QueryBuilder.execute(), new abstract methods execute[Before/After]QueryBroadcast()

…pression()

Drivers must explicitly return "NULL" string because Array.join() ignores null values
unlike string concatenation that was used previously.

More efficient method of finding the columns that are contained in a given entity object.

Previously the object was recursively scanned for keys and all were converted to property paths,
then for every property path the columns were searched to find a matching one. Now the columns are
selected as the object is scanned, and since ownColumns is searched instead of all columns it is
more efficient.

…dering

For certain drivers where the native parameters are not indexed (e.g. MySQL, "?")
the parameters which are found at the start of a query - specifically in UPDATE
SET param = ? - must be placed at the start of the native parameters objects. For
drivers where the parameters are indexed, the order must match the order of param
variable creation (e.g. Postgres, ":1").

This allows each driver to specify whether it cares about parameter order, allowing
UpdateQueryBuilder to reorder params if necessary.

…ryRunners

While SELECT queries tend to result in objects containing columns and their values,
DELETE/INSERT/UPDATE queries all have different outputs depending on the driver. This
moves the processing of those outputs and their mapping to the [Delete/Insert/Update]Result
objects to the driver QueryRunners so that it can be altered without changing the QueryBuilders.

Greatly simplifies getEntityValue, setEntityValue and related functions. Previously embedded objects
were explored using recursive functions and array shifting, which is now replaced with simple for of
loops. Improves readability and possibly performance.

* New QueryBuilder.createColumnValuePersistExpression() that converts (column, value) to expression string
    * Previously mostly duplicated between InsertQueryBuilder and UpdateQueryBuilder
    * SoftDeleteQueryBuilder now even closer to UpdateQueryBuilder

* Entity column and raw object key based expression generation also combined
    * Previously some duplicated code, e.g. function values always treated as raw SQL

* InsertQueryBuilder.getInsertedColumnsOrKeys() now returns string[] if using raw objects
    * Now supports extracting columns from multiple raw objects, without predefined insert columns

* Static ReturningResultsEntityUpdator.generateUUIDParameterName() for extracting generated UUID
    * Ensures that InsertQueryBuilder uses correct parameter name

Replaces string concatenation with joins in all query builders. No longer need to keep track
of whether a particular element of an expression should have a space before or after it.

Does not seem to do anything differently to Object.assign().

Introduce Mutable util to access readonly properties of classes when initializing.

…vers

Some drivers require functions such as ST_AsGeoJSON when persisting or selecting columns, this
moves the wrapping of the persist/select expressions from the query builder to the driver.

SAP HANA doesn't support null values as parameters so they are converted to the
raw NULL value. This moves that conversion from query builder to SapDriver.

Makes Driver.parametrizeValue() an optional function, currently implemented
only by SqlServer. Other drivers can now also add additional information to
their parameters if necessary.

…yBuilder

Moves all functionality from SoftDeleteQueryBuilder to UpdateQueryBuilder except the
"from()" function used to specific "soft delete FROM table", because a similar method
does not currently exist for UpdateQueryBuilder.

…aryGeneratedColumn

…One/@manytomany

In preparation for "virtual"/computed columns, call internally generated columns "internal"
rather than "virtual" to avoid confusion.

…ction)

All options in @column() define a real column except for embedded. This adds an additional
@Embedded decorator for more explicitly defining embeddeds while still maintaining the
option in @column().

* Introduces new type to describe the fields parameter of an @Index or @unique.
* Allows (type) => [type.column] syntax inside embedded

…yMetadatas()

* Removes unnecessary array pushing/slicing
* Matches buildMigrations()/buildSubscribers() more closely

…elete

* Rename ModificationQueryBuilder to AbstractModifyQueryBuilder (UPDATE/DELETE)

* New AbstractPersistQueryBuilder for INSERT/UPDATE/DELETE
    * Common code for RETURNING expressions
    * Common code for INSERT/UPDATE value expressions

* Move UpdateDateColumn, VersionDateColumn, etc to value expression calculation
    * Matches InsertQueryBuilder behavior

refactor: driver: Move database specific EntityManagers to driver

Accidentally ammended during rebase

…lags and generators

Introduces `DriverConfig` and `DriverQueryGenerators` interfaces that include various
flags that drivers can use to customize behavior of the built in functionality. This
decouples these built in features from the drivers themselves, moving towards the
possibility of having each driver in a separate package.

…ransformer

* InsertQueryBuilder.orUpdate() now takes 3 parameters, overwrite columns, column values and conflict condition
    * Overwrite either specific property paths in array or `true` to overwrite all
    * Values same as UPDATE query values, replaces overwritten columns
    * Conflict see onConflict()

* InsertQueryBuilder.orIgnore() now takes 2 parameters, ignore and conflict condition
    * Ignore boolean whether to add IGNORE / DO NOTHING, no longer accepts statement
    * Conflict see onConflict()

* InsertQueryBuilder.onConflict() now accepts either raw expression or property paths array
    * For Postgres/Sqlite ON CONFLICT ...

* EntityManager.upsert(), Repository.upsert(), BaseEntity.upsert()

Fixes: typeorm#1090