Fix how ORM sets object name, object plural name, and table name.
- patch Kohana's ORM class to allow predefined object name
(see http://github.com/kohana/orm/pull/81).
- revise ORM::_initialize() override to set object name instead of table name.
Use "model_relationship" event in ORM::_initialize() override to set relationships.
Revise Item/Tag relationship to use "model_relationship" event.
Revise search to use SearchRecord/Item model relationships.
Revise comment to use Comment/Item model relationships.
Revise Model_Log to overload get() instead of __get().
Revise User/Group relationship to use "model_relationship" event.
Revise documentation comments in ORM::delete() override to use the "model_relationships" event.