Configurable Content Providers

- Added configurable content providers
- Removed 8 built-in content providers
- Added 8 default content providers to config
Content Providers can be disabled through admin

Makes the built-in content providers togglable from the admin
ui. Now you can turn on/off providers as well as add additional
providers dynamically.
Merge in changes from upstream/dev
Merge pull request #1078 from InfinitiesLoop/dev

Configurable ContentProviders