Created the new effects for represent tweens and tracks
Added classes to create a tween by means of an animation effects.
Added TrackEffectExecutor.
Added class and processor to keep multiple effects tracks.
Added the necessary initializations for the new classes.
Added a test for Animation, TrackEffect and the AnimationsEffect
Added Resource to the Model as a wrapper around the resources with a dirty bit.
Adds test and widgets fixes after the model changes.
EditScene action sets the id of the scene as the modified resource.
Adds ResourceModifiedListener.
Adjusts Save action after the recent changes.
SaveGameTest improvements.
Now the TimedEffect has only a effect and not multiples.
Also done other minor changes.
Small fixes after rebase.
Merge pull request #697 from gorco/TimelineEffects

Timeline of standard effects and animation effects.
Merge pull request #696 from RotaruDan/savingSystem

Saving system improvements