Enable locking on some perf test types
Fix locking bug in ExpectedValueChecking*

ExpectedValueCheckingTransactions with locks on more than one store
only checked locks on one of the stores at mutation time and ignored
locks on the rest of the stores.  This affected Titan when it called
EVCSManager.mutateMany after acquiring locks on multiple stores.  It
could also have theoretically affected Titan if it called EVCS.mutate
on different stores but using the same transaction, though I don't
know whether core contains any such cases -- just that the potential
to exercise the bug would exist there.
Merge branch 'titan05' of github.com:thinkaurelius/titan into titan05
Refactor EVCS lock-checking logic

This change is mostly a refactoring and javadoc commit in the
ExpectedValueChecking* classes.

However, it also includes a functional change.  Previous to this
commit, locks taken on stores without any mutations (stores treated as
read-only) would be ignored.  Now locks are checked regardless of
whether the underlying store has any data mutations waiting.
Add test of ExpectedValueCheckingStore/Tx