New Field: ChosenListBoxField

This Field has the same functionality as the ChosenDropdownField but
works as a replacement for the ListboxField
Merge pull request #13 from jrast/feature/ChosenListboxField

New Field: ChosenListBoxField
MINOR: added composer.json
MINOR: Error in JSON
Update composer.json
MINOR: use $extraClass in BootstrapFormAction
Merge pull request #15 from Zauberfisch/patch-1

MINOR: use $extraClass in BootstrapFormAction
MINOR: Remove whitespace
MINOR: Update composer.json to use new naming convention
ENHANCEMENT: Apply bootstrap forms to UserDefinedForm and Security