[IMO] MediaListPlugin.

* All test OK
* Consider performance
Merge branch 'master' into imo-medialist-plugin
Add test.

image, body, heading => left image and body
Add tests.
Refactor medialist plugin
Modify comment
Merge remote-tracking branch 'origin/imo-medialist-plugin' into feature-medialist-plugin

Conflicts:
	app/lib/Toiee/haik/Plugins/MediaList/MediaListPlugin.php
	app/tests/Toiee/haik/Plugins/MediaListPluginTest.php