Renamed ChangeSceneNote to ChangeNote, now also accepts the first argument as a Note.
Changed ActionForTextFieldListener to use the new ChangeNote action correctly.
Selected the element prior to start editing him.
Now the elements correctly change title and description.
Now ElementButtons correctly display the title and the description.
Simplified eAdventure Mockup UI buttons constructors.
Removed some unused imports and other minor stuff.
Fixes #435
VariablesSystem renamed to VariablesManager
VariablesManager is not a System anymore.
Also: some outdated javadoc fixed along the way
VariablesManager added as a field of EngineApplicationListener that is passed down to GameLoader, EngineInitializer, etc.
Accommodating API changes (review not needed)
Package ...engine.systems.variables moved to ...engine.variables (review not needed)
Fixes #204
Merge pull request #436 from jtorrente/issue-435

Fixes #435
Merge pull request #430 from RotaruDan/selection

Change element title/description functionality.
Model now uses complete paths as ids. Also, some convenient methods
Fixed classes after changes
Fixed tests
Added javadoc to GameLayers