Locking refactoring and javadoc cleanup

* Moved AbstractLocker & AbstractLockStatus up from
  locking.consistentkey to just locking

* Added and rewrote javadoc on Locker.  It's now up-to-date with the
  current inerface semantics

* Updated ConsistentKeyLock* javadocs

* Deleted unused classes made obsolete by locking refactoring
Javadoc updates

Moved locking's package-level javadoc into ConsistentKeyLocker and
rewrote it
Javadoc and unused class cleanup
Moved LocalLockMediator classes

These classes are not ConsistentKeyLocker-specific, since they are now
used indirectly by both ConsistentKeyLocker and AstyanaxRecipeLocker.
I moved them from locking.consistentkey to locking, alongside the
AbstractLocker class that directly relies on them.
Javadoc fix in LockerState
Renamed ConsistentKeyLockStore/Transaction

These classes contain no actual locking logic.  That's delegated to a
Locker instance.  They are only responsible for expected value
verification at this point.  I renamed them to
ExpectedValueCheckingStore/Transaction.

This commit also adds another ConsistentKeyLockerTest method.