move to oxlos.com

resolves #17
moved activities and staff apps to oxlos package

part of #12
show staff completed occurrences as well as total
added per-user stats to staff dashboard
added admin for activities app
template tag for user stats
use user stats template tag on staff dashboard
better call to action on homepage
show adoption level on staff dashboard
show timestamp of last event on staff dashboard
protect against no event
moved generic templates to oxlos

part of #12
factored out head title

part of #12
moved more generic templates to oxlos

part of #12
reorder apps so oxlos can override theme
pass in both occurrence state and activity state

Previously occurrence state was passed in to activities but it was
incorrectly called activity state. This fixes that problem and also
adds the real activity state.
new activity: greek keyboard

learn and practice the Greek keyboard layout
don't show instructions if not first time

was a problem when a session was interrupted and the activity continued
moved custom activities to package

This is step one in splitting them up into separate modules.
organized activities into different modules