Added and changed icons and skin.
Used the new icons.
Merge pull request #733 from gorco/iconsAndSkin

Icons and skin
Reduces threshold and distance tolerance in MockupImageProcessor.
Disables the collider drawing while playing in Mockup.
Fixes saving system in eAdventure Mockup.
Improves SceneItem and ProjectItem. ScenesView and ProjectsView fixes.
Fixes BrushStrokes and MeshHelper. Improves PaintToolbar.
Improves MockupSceneEditor: disables multiple selection and nested group edition, pinch and zoom functionality, clipping, etc.
Adds ElementContext to the Edition view and associated functionality: clone, erase, toFront, toBack, etc.
Adds OthersWidget.
Some UI widgets improvements.
Views improvements.
Minor changes.