generate newUserSelections as computed property
remove old newUserSelections property
Fixing validation of newUserName; removed validation of newUserSelections temporary

Therefore has to move creation of new user from view to controller. ember-validations had problems with views.

Removed not working validation of newUserSelections temporary.

isValid is false until a property observed by ember-validations got changed; therefore form is not valid until username got changed even if anonymous users are allowed. Will be fixed by validation on new user selections.
observes in condition validator is not needed
add validation for user selections
fix bug vor ember-validations on startup

have to rerun validation manually when encryption key is present in model
conditional validation of everyOptionIsAnswered depending on poll setting forceAnswer

Fixes #21