Add org.jooq.Trigger to support custom callbacks to be configured

[lukaseder]

In legacy environments where new database triggers cannot be implemented easily, jOOQ shall offer custom trigger functionality, mimicking commonly known database trigger functionality.

These jOOQ triggers allow for intercepting basic DML statements, such as DELETE, INSERT, UPDATE. More sophisticated DML statements, such as MERGE, INSERT ... SELECT, INSERT ... ON DUPLICATE KEY UPDATE may not be supported. Batch execution may not be supported either, or the batch statement may be split into several single statements.

On interception, i.e. on firing of a trigger, the trigger may execute custom Java code (including custom SQL / jOOQ code) BEFORE, AFTER or INSTEAD OF the intercepted DML statement.

In addition to what SQL databases offer, this trigger API also allows for intercepting SELECT statements, and perform BEFORE, AFTER or INSTEAD OF actions on those.

Some examples:

• http://docs.oracle.com/cd/B28359_01/appdev.111/b28370/triggers.htm
• http://msdn.microsoft.com/de-de/library/ms189799.aspx

[lukaseder]

This feature is better represented by the new client side computed columns feature: #13444