"layer" operator added.
Format: (layer sLayerName)
Returns: the EngineEntity associated to the given layer
API changed = refactorings
Minor typo
TweenSystem listens to entity removal events so tweens of removed entities are killed.
This is important since entities are pooled
Test updated
Moving updater to editor-desktop
Added tooltip and tooltips manager
Added tooltip manager to desktop editor
IconButton implements Tooltip
Tooltips for the main toolbar
Merge pull request #527 from jtorrente/fix-415

Tweens of removed entities get killed
Merge pull request #529 from jtorrente/fix-426

Moving updater to editor-desktop
Merge pull request #524 from jtorrente/getlayerop

Get layer op
Added background panels
Fix in AddSceneElementFromResource
Added blank background to topToolbar
Added modalsContainer to Views

viewsContainer (container for differente perpsective) is different from
modalsContainer (container for context menues, that also contains the
main toolbar and viewsContainer).
Refactoring after changing Views constructor
Merge pull request #521 from anserran/tooltips

New tooltips mechanism
Merge pull request #518 from anserran/backgrounds

Added some backgrounds to widgets; Fix for context menues