fix table alteration on Drizzle
fix altering column from notnull to null in Oracle
fix dropping table without autoincrement trigger in Oracle
Merge pull request #468 from deeky666/fix-oracle-schema-manager-drop-table

Fix dropping table without autoincrement trigger in Oracle
Merge pull request #467 from deeky666/DBAL-472

[DBAL-472] Fix altering column from notnull to null in Oracle
Merge pull request #463 from deeky666/fix-drizzle-table-alteration

Fix table alteration on Drizzle