less memory-intensive signing and verification of large files.  Future use for signing zip files.
first pass, through Django
refactoring code into (optional) settings
forgot migration file.
fixing username / user bugs
workaround for new users; better fix to come\!
invalidating cache when settings change.
Merge branch 'release-0.10' of github.com:learningequality/ka-lite into local_password_hashes

Conflicts:
	kalite/settings.py
Merge branch 'release-0.10' of github.com:learningequality/ka-lite into local_password_hashes
refactoring for cleaner implementation, better validation.
Bump build number.
updating to use efficient hashlib functions, and add tests.
setting attempts fully on every request, rather than incrementing.
avoid incrementing in videos for total_seconds_watched; set explicitly every time.
fixing trailing comma, which breaks some builds of IE
fixing #662, cleaning up code surrounding knowledgemap
fixing #578
distributed servers do not have access to sync sessions from other distributed servers.  So don't suggest we know something about them in the zone_management page.
forgot to migrate to None, rather than hard-coding values in view
approximating @jamalex algorithm in Python