Refs #340: Remove forms.css

I clicked around our contrib app pages that have forms and looked at
what styles were applied (using Chrome Inspect Element) and didn't see
anything from forms.css being used. I conclude that bootstrap is
overriding everything we were setting in forms.css, so it's redundant.
Refs #340: Move old stylesheets to locations app

- Stop loading old stylesheets in base RapidSMS template
- Move the old stylesheet files to the locations app
- Load the old stylesheets from the locations app's base template
- Modify the table styling in a few other contrib apps' code to take
  advantage of bootstrap
- Add a backwards incompatibility note to the 0.15 release notes.
Suggest PyPI classifiers and license
Add to suggested classifiers
Merge branch 'feature/suggest-pypi-classifiers-and-license' into develop
Revert changes to releases/0.15.0.rst
Merge branch 'develop' into feature/340-drop-forms.css
Update releases/0.16.0.rst
Merge branch 'feature/340-drop-forms.css' into develop