Removing skins from repository
Adding Generate skin atlas maven plugin

The maven plugin check if it is needed to generate the atlas (the target
location does not contain a generated skin's atlas) and generate it.
Fixes #253
Moved Ttf2FntGenerator to ead-maven-plugin.
Added mockup sources and images.
Added mockup font generator.
Merge pull request #463 from anserran/master

Removed unnecessary index notification
Merge pull request #449 from imartinezortiz/skin-generator-maven-plugin

Skin generator maven plugin; thanks to Ivan & Christian
New assets for the skin
Added test to facilitate launching parts of the editor separately
Renamed ActorEntity to EngineEntity
Added an engine instance and a shape renderer to controller
GroupEditor: Added enteredgroupeidtion and endedgroupedition event
Some changes to make EditorUI work
Bug fix in ListCommand. forceCombine added to CompositeCommand
Added parent to Renderer Actor
Added EditorImageComponent and its processor
Added ModelActions to perform changes in groups edited in GroupEditor
Added tests for group commands
Added SceneEditor view
Added executable test for SceneEditor