Correctly parse BroadcastReceivers that don't have intent filters defined

Fixes #1223.

I also removed `getReceiverCount `, `getReceiverClassName`, `getReceiverIntentFilterActions`, and `getReceiverMetaData`. It does change the public API of `AndroidManifest`, but you can accomplish the same thing with `getBroadcastReceivers`. Manifest related classes were also moved to a new org.robolectric.manifest package.