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