Fixing MSSQLDatabase to conform to dev/build change detection

This involves changing a few things around so that it's closer to
how the MySQLDatabase adapter works. indexList() should return an
array in the same format instead of using arbitrary "indexname"
and "spec". indexNames() has also been introduced to MSSQLDatabase
so that we can drop all indexes (except for fulltext and primary key
indexes) on a table when altering the table columns, this helps when
constraints not directly related to a modified column refuse to allow changes.