Fix dropping foreign key multiple times with test

In some cases the Comparator class returns multiple drops for the same foreign key.
Specifically, in case you have two tables, A & B, with A having a foreign key FK
referencing B, if you drop table B, the resulting diff shows this FK twice,
once on the diff->orphanedForeignKeys array as we're deleting B, and another on
the diff->changedTables array as table A is also being modified. As a result of this you
get the DROP FOREIGN KEY instruction twice in the final SQL.
Fixed typos, finished comment on test and added new assert.
Fix bug with CamelCase table names
Merge branch 'DBAL-360' into 2.3
Removed unsigned integer test as SQL Server doesn't support unsigned integers.
Merge branch 'DBAL-354' into 2.3
Delete always content from table master_slave_table between tests.
Merge branch 'GH-203' into 2.3
Add schema changes for length for postgres
Merge branch 'DBAL-323' into 2.3
Fixed issue if comment contains quotes. It sould duplicate the quotes in MySQL platform.
Merge branch 'CommentQuotes' into 2.3
Merge remote-tracking branch 'origin/2.3' into 2.3
Issue: Default table options are not used
- Fixing issue, key name corrected
Merge branch 'DBAL-378' into 2.3
Fix SQLServerPlatform adds unique constraint to ADD PRIMARY KEY statement

This will only happen when adding primary keys via ALTER TABLE
Add test for SQL Server ALTER TABLE primary key issue
Update condition to use CS
Merge branch 'DBAL-379' into 2.3
DBAL-374 - Initial testcases