Cleanup, models and others

This fixes these bugs:
- [bug 1080650](https://bugzilla.mozilla.org/show_bug.cgi?id=1080650) - Add Protected Flag to features
- [bug 1082006](https://bugzilla.mozilla.org/show_bug.cgi?id=1082006) - Enforce one Support per Feature/Version combo
- [bug 1082023](https://bugzilla.mozilla.org/show_bug.cgi?id=1082023) - Support cache should update on save
- [bug 1082044](https://bugzilla.mozilla.org/show_bug.cgi?id=1082044) - Drop browser.icon property.

Also fixed a typo and JSON issue in app.json, without a bug number.