New icons
Some strings
Avoid irrelevant enable events in actions
Bug fix in tab widget
Added WidgetUtils to encapsulate common methods to create widgets
Added MirrorSelection action
Added RotateSelection action
Added format tab to scene ribbon
ListEvent contains the list owner
Changes to adjust to the new API
Merge pull request #564 from anserran/ownerevents

Now ListEvent contains a reference to list owner
I18N strings.
Small fix after recent EditorGameAssets#resolve() changes.
Removed CombinedAction.
Small ImportEntity bugfix.
Now EditionContext is being setted before editing an element.
Size improvements to DescriptionCard widget.
Created LibraryScreen.
Changed RepositoryManager to work with libraries.
Added clipping in MockupSceneEditor.