Remove legacy RestrictedPriorityQueue (not the one used by
AgreementSite).
With RPQ gone, RPQInterface is also unnecessary.
In IV2, SiteMailbox no longer needs to know about the command log.
Also, clean up some stale imports.
Get rid of unused logHeartbeat method on CommandLog.
Hey, look, we don't log old-style legacy faults anymore, either.
IV2 command logging doesn't have or care about the fault sequence
number.
Merge pull request #439 from VoltDB/rpqpurge

Remove legacy command logging code
Legacy DTXN purge: delete unused-in-IV2
MultiPartitionParticipantTxnState, propogate consequences.
Legacy DTXN purge: Delete RecoveringSinglePartitionTxnState, which was
apparently not even used by legacy DTXN.
Legacy DTXN purge: Remove unused-by-IV2 SinglePartitionTxnState
Legacy DTXN purge: Remove unused-by-IV2 ReplayedTxnState and junit
test.
Legacy DTXN purge: Remove unused SimpleDtxnInitiator.  All of its
threads were hacked off in an elastic-motivated commit set earlier.
Legacy DTXN purge: Remove unused-by-IV2 DtxnInitiatorMailbox and junit
test.
Legacy DTXN purge: Remove unused-by-IV2 ExecutorTxnIdSafetyState.
Legacy DTXN purge: Remove unused-by-IV2 WorkUnit.java
Legacy DTXN purge: Remove SiteTransactionConnection.
- Remove legacy constructor for TransactionState
Legacy DTXN purge: Remove unused-in-IV2 InFlightTxnState and junit
test.
Legacy DTXN purge:  TransactionState and its remaining subclasses no
longer require or implement the handleSiteFaults() method.
schemachange app: add duration and change iteration count
Eliminate another unused TransactionState method.