Connection#insert(),  Connection#update() and Connection#delete(). Closes GH-271

DBAL-54 was fixed in commit 3d55dc8e by
changing SQL queries order. However it was later reintroduced.

This patch uses a different, more future-proof way, approach by using
DROP SEQUENCE ... CASCADE syntax, and thus does not depend on queries order.

Change Oracle sequence generation to match what is being created by ORM and other platforms in the form of $table_$column_SQL instead of $table_SEQ

Choose between TINYBLOB, BLOB, MEDIUMBLOB and LONGBLOB based on the length of the field.
Behaves the same way as the TEXT type declaration.

This should be 65535 (2 ^ 16 - 1) in stead of 65532.
Modified docblock to show the max lengths.