improve user_line
Merge branch 'user_line_13.24'
implement extension_dao.find

Conflicts:
	xivo-dao/xivo_dao/data_handler/extension/dao.py
	xivo-dao/xivo_dao/data_handler/extension/tests/test_dao.py
remove tests that need user_line.user_id to be NULL
remove dependencies on line_extension
Merge branch 'master' into package_builder

* master:
  remove dependencies on line_extension
  remove tests that need user_line.user_id to be NULL
  implement extension_dao.find
  improve user_line