Now the PaintButton and EraserButton of ElementEdition are in other toolbar.
This toolbar appears when pressed add/paint new item.
Fixed visibility tool bar bug.
Removed some unnecessary classes
Added file chooser dialog and widgets related
Substituted old file chooser with new file chooser
Fixed minor bugs and added some comments
Small improvements to the new tool bar.
Merge pull request #287 from RotaruDan/PaintView

Paint view
Added fileChooserListener to constructor; some javadoc;
Converted fileComparator to private static class
Small bug fix saving FILE_CHOOSER_LAST_FOLDER preference
Efficient rendering of vector-based shapes and lines

- Stages replaced with EditorStage, in charge of a second ShapeRenderer pass
  (similar to the original SpriteBatch pass)
- Actors that wish to draw vector-based in this second pass must implement
  ShapeDrawable
- Replaced all "scaled empty boxes" with a 1 px border rectangle
- Fixes #148 (object-handles resizing themselves)
- Accesses Group's transforms to avoid additional transform matrix creation
Properties renamed to .props to avoid encoding issues
Fixes single hardcoded .properties reference (in I18N)
Fixes a few bad encodings
Merge pull request #292 from manuel-freire/properties-to-props

Properties to props
Actions separated in two packages: model actions and editor actions
Added EditorAction and ModelActions, and associated controllers
Testing invalid arguments in actions
Added default mechanism to validate arguments
Created InvalidArgumentsException