Fix for DBAL-158, double precision not working with sqlite.

DDC-1337 - MySQL commits transaction on DROP TABLE, need DROP TEMPORARY TABLE. Added tests, looks like oracle commits transactions on CREATE TEMPORARY TABLE. I dont know how to fix it.

Patch for OCI8Statement to support param[0] being null. Switched isset to array_key_exists. Added test that demonstrates the bug and confirms the fix.

DBAL-132 - Make Table::addUnnamedForeignKeyConstraint() generate a name based on the input, @deprecated addUnnamedForeignKeyConstraint and addNamedForeignKeyConstraint.

DDC-1282 - Remove overprotective casting of days/months to integer, which prevents passing columns as days. The platform is not responsible for escapsing, the DQL parser already does it way before generating the sql statements.

DDC-1271 - Fix date diff in PostgreSQL when timestamps are passed by casting everything into dates explicitly.

This reverts commit 0d2af886, reversing
changes made to eb0a4615.

DDC-1271 - Fix date diff in PostgreSQL when timestamps are passed by casting everything into dates explicitly.