For ENG-5803, add support for disabling compaction
Fix a correctness issue with disabling async logging and fix a potential performance issue with disabled log levels still generating tasks for the log thread
Fix typo in previous commit for log4j async improvements
Merge pull request #1161 from VoltDB/log4j_async_check

Log4j async check, don't create a task of the log level isn't set
Merge pull request #1164 from VoltDB/ENG-5803

For ENG-5803, add support for disabling compaction
Update doc PDFs.
One minor addition to the UsingVoltDB.pdf
ENG-5941 Fix recovery breakage due to new catalog version check.
Merge branch 'master' of github.com:VoltDB/voltdb
ENG-5878: Print an error message if a system has older python than 2.6.
ENG-5947 ENG-5948 Misc. catalog upgrade fixes/tweaks.
Merge branch 'master' of github.com:VoltDB/voltdb
Merge branch 'master' into ENG-5571-subquery