Lollipop support

Brings Lollipop support to Apktool.

- [x] API 21 support
- [x] API 21 tests
- [x] API 20 tests
- [x] anydpi qualifer
- [x] BCP-47 support
- [x] Support for `TYPE_DYNAMIC_REFERENCE`
- [x] Updated aapts
- [x] Updated internal frameworks to API 21