Fix creating indexes for renamed columns and updating foreign keys for renamed parent tables in SqlitePlatform

- Fixing issue, key name corrected

Remember to close temporary connection in PostgreSqlSchemaManager::dropDatabase() and PostgreSqlSchemaManager::createDatabase()

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.

Unsigned column properties were never set. In consequence all migrations diff were trying to change the column definition when it was already changed.