refs #693, refs #716, refs #720, refs #623
fix rollbackRefOp and purgeEntryFromOplog for spilled transactions,
improve test coverage of initial sync,
make a unit test for rolling back different oplog entries
make rollback_simple.js not be flaky
refs #716, some fixes
Merge branch 'bugfixes/tokumx-1.3' into releases/tokumx-1.3