Merge in changes from master
Update version
Organize client files
Update libraries
Update base documentation
Refactor model
Begin refactoring theme module
Finish refactoring theme modules
Resolve migration issues
Enable show/hide admin metaboxes
Optimize themes collection initialization
Add base object class
Add Content_Handler class
Add base collection class
Add content handler collection class
Initialize base collection array as NULL
Rename Content_Type to Content_Handler
Content Handlers: Add custom `add` method
Rename `Content_Handlers` class file
Enable initialization hook for `Base_Collection`