ENG-6846: Add physical memory to memory stats.
Merge pull request #1658 from VoltDB/ENG-6846

ENG-6846: Add physical memory to memory stats.
Update PDFs for 4.7
ENG-6893 - Fix deprecation warning in some Pythons re. exception.message.
Merge pull request #1664 from VoltDB/notest-ENG-6893-cli-exception-message

ENG-6893 - Fix deprecation warning in some Pythons re. exception.message...
Merge remote-tracking branch 'origin/master' into ENG-6071-changeempty