Removed front end stylings from Form Builder.

This is at the behest of the designers and it is a good idea.  We should
never have had anything but minimal structural CSS for the frontend to
being with.

We might want to consider removing some of the CSS files from [Page Builder](https://github.com/fusionbox/django-widgy/tree/master/widgy/contrib/page_builder/static/widgy/page_builder) as well.  Here is a list of candidates for removal:

- https://github.com/fusionbox/django-widgy/blob/master/widgy/contrib/page_builder/static/widgy/page_builder/googlemap.scss
- https://github.com/fusionbox/django-widgy/blob/master/widgy/contrib/page_builder/static/widgy/page_builder/tabs.scss (just the padding declaration)
- https://github.com/fusionbox/django-widgy/blob/master/widgy/contrib/page_builder/static/widgy/page_builder/video.scss

cc @justinstollsteimer, @eball-babois