Minor refactor in events
Added command to add/remove entities from model
Updated Index to process new event type
Added new scene model action
Added method to add entity event listeners
Added notion of transparent commands. Also fixes #143 with commands test
Added SelectionCommand
Added SetSelection action
EditState.sceneorder is udpated in NewScene
Merge pull request #479 from anserran/selectioncommand

Added SelectionCommand
Renamed EntityCommand to RootEntityCommand
Merge pull request #473 from anserran/newscene

NewScene model action, along with a new commands to add/remove model entities from the model