Regarding #38 #39:

- Deleted large redundant portions of BallotStore.java. Currently holding some code that may be useful in reconstructing Tallier in Precinct.java
- Added a provisional check to VoteBoxBooth.java that is used during ProvisionalBallotCommitEvent and BallotCommitEvent to make sure authorisations are present
- Implemented a new class: PINValidator.java (SINGLETON). Model.java uses this class to deal with all PIN -> PID actions and no longer has to deal with PIN expiration and such in its code  body
- Got rid of or moved unnecessary fields
- Added a pollsClosed() method to Precinct.java to deal with challenging/spoiling committed ballots when polls close
- Fixed the creation signature on Preinct.java