Reverted ignore rule for errno:11 fix from wsgi.server (causing some side effects).

This reverts commit 25400ee766f416f529e381c391d9be9e53b3b2ef.
Updated observer to not mess up class attributes when Observable is applied.
Updated datalayer parameters order for update operations to accomodate parametrized queries.
Added parametrized queries to datalayer update and delete operations.
Implemented DataMapper update and delete methods.