Fix getTableConfig not returning all the primary keys

[Angelelz]

close #1285

• Added a loop through all columns looking for primary keys to add it to the primary key array.
• I also added the unique constraints found in the columns to the list of constraints.
• Added integration tests.

It seems like the .primarykey() method on the column builders was not really doing anything, unless drizzle-kit was getting the primary key directly from the column.config.primaryKey.