* Move merge component's opts with distro, persona, etc to cfg.py
* Implementing YamlMergeLoader
* Add unit tests for correct updating cached and processed opts data
* Add unit tests for YamlMergeLoader
* Fix redefinition process in personas
* Add documentation to YamlMergerLoader docstring
Change-Id: Ie491defca3df09d763081799d551cef8c2128701