Feature Request

Describe your feature request related problem:

Support backing up multiple tables in a single command without needing the --backupts trick.

Describe the feature you'd like:

A simplified version of #173. We support the following commands to backup/restore multiple databases or tables.

./br backup database --db firstdb --db seconddb 
#                                 ^~~~~~~~~~~~~
./br backup table --???? 'firstdb.firsttable' --???? '`second.db`.`2,tbl`'

Because the table name can contain a ., we need to support quoting by `.

Unresolved question:

• Should we change the behavior of database --db 'db1,db2'? (currently backing up a single database named "db1,db2"
• Should we change the behavior of database --db '`db`'? (currently backing up a single database named "`db`"
• What should the --???? parameter be named?
• Should we keep the table --db db1 --table tbl1 form?
• Do we want to support table --???? 'db1.tbl1,db2.tbl2'?
• Do we want to support table --db db1 --???? tbl1 --???? tbl2?
• Do we want to support table --db db1 --db db2 --???? tbl1 --???? tbl2?
• Should we support ANSI quotes table --???? '"db1,db2"."tbl1,tbl2"'?
• Should we reject if the inputs aren't proper identifiers table --???? '!@#$.%^&*'?

Describe alternatives you've considered:

Don't support this and go straight to #173.

Teachability, Documentation, Adoption, Migration Strategy:

If we decide to name --???? as --table we'll need to rewrite all documentations.