allow upgrades via python-based install script
fixing two bugs--one in detecting install_clean, the other in assuming that meant a db file existed.
Really obey the command-line args (used only if in non-interactive mode)
Merge branch 'release-0.10' of github.com:learningequality/ka-lite into upgrade_via_install
Merge pull request #598 from bcipolli/upgrade_via_install

Upgrade database via install.py