Further enabled various UI components in the dynamic-forms app

* verbose_names and help_text added
* answer attribute of AE now takes and returns iter of int for
  categorical questions
* readable_answer translates iter of int to QuestionChoice.value
* Modified QuestionAdmin by inlining QuestionChoice
* (TODO) disabled modification checks on QuestionChoice to enable
  QuestionAdmin and inlined QuestionChoice to work
* don't republish already published questions when publishing a
  Template
* add bootstrap-datepicker, revert SelectDateWidget to DateInput
* add and enable django-crispy-forms and associated layouts
* create, submit and publish form actions