[WIP] Add layout data interface
Add LayoutDataInterface
Add delete method to LayoutDataInterface
Modify comment doc of get method
Rename method and add a method.

Rename methods to CamelCase: *_once -> *Once
Add method setAll
Add Tests
Fix test
Modify parameter name of prependOnce
Fix tests
Add ThemeFacade and implement.

* register ThemeServiceProvider
* implement ThemeManager
* add ThemeFacade
Merge pull request #45 from toiee/layout-data-interface

Add layout data interface

Enable ThemeFacade