Basic code for doing deletion stubs locally.  Will not propagate remotely.
Removing is_deletable code.
Remove need for add_syncing_models
Introduce (debug) settings to allow deletions and viewing of deleted objects.
Introduce all_objects manager, which will always return deleted (and not-deleted) objects.
Work-around for validation issue on save, where deleted foreign keys can't be found (they're hidden!)
Don't update userlog info by default--otherwise, programmatic Django save-related stuff fails (or becomes really hard to do generically).
Missed removing a reference to `is_deletable`
Test fixes.
Add local_settings_secrets.py to .gitignore
Make # queries expected for admin login more flexible.
Move app static libraries to static-libraries.
Move ka-lite app static libraries to static-libraries.
Clean up use of video_id and youtube_id in khanload.
Move function to updates (breaks main dependency on i18n, puts function in only place where it's used (it could have gone in i18n as well))
Clean documentation and use of youtube_id in main code.
A little bit of cleanup.
Don't make an additional embedded query in deleting sync sessions.

Especially as this breaks MySQL.
Don't have a maximum number of syncsession records by default.
Merge pull request #142 from jamalex/fix_syncing

Fixes to deleting older sync sessions