Read State, Parse CommentRSS, Parcelable

- Now saves read state, efficiently
- Custom SparseBooleanArray supporting Parcelable
- Read APIs
- Protected getInstance() method
- Testing read states
Separate package for PkRSS

Moved all files related to PkRSS to its own package. This helps expand protected methods to Article/Database objects and will make it easier to transition into a separate library later.