- Added fadeIn to animation JS service.
- Updated overlay to use anim service and to recieve a callback for
after-anim actions.
- Updated code editor popup to refresh Codemirror instance layout after
animation has completed.
Fixes#1672
- Codemirror mode mapping value can now be a function to dynamically set
mode depending on actual code content.
- Used above system to set php mode type, depending on if '<?php' tags
exist in content.
Closes#1557
