update wicket-jquery-selector version.
proposed solution for issue #414
FormGroup should not implement IFormModelUpdateListener

- this interface should only be implemented by form components
  to update their _own_ model
- the wicket Form already visits all its child form components
  and call their updateModel method
  -> the updateModel method of the FormGroup causes that the
     updateModel method of each of its children gets called twice
add test cases (issue #414)
Merge pull request #418 from l0rdn1kk0n/issue-414

improve Date conversion between java/js
Merge pull request #416 from romueller/master

FormGroup should not implement IFormModelUpdateListener
add test for duplicated updateModel call
upgrade wicket-jquery-selector to 0.1.2
add Darkly theme
Merge pull request #419 from tahitiangabriel/master

add Darkly theme for Bootswatch
fix trailing comma closure compiler error

fix google closure compiler error with trailing comma in array
Merge pull request #423 from subes/master

fix trailing comma closure compiler error
Merge branch 'master' into wicket-7.0.0-M1