Cherry-pick partial sync trigger stuff from endomondo-2
Fixed potential weirdness resulting from modifying activity list during iteration for deferred services.
Rearranged service_base, added polling infrastructure
GC partial sync triggering logic
Well, at least I didn't commit pdb.set_trace()... Still laughing though.
Cache GC cookies by email too, not just service records
Polling worker & scheduler
Un-break services that aren't Garmin Connect
Ensure partial sync trigger is subscribed during synchronization, unset said flag on completion
Deploy prep
Added page explaining Garmin Connect user shenanigans
Merge branch 'gc-user-watch'

* gc-user-watch:
  Added page explaining Garmin Connect user shenanigans
  Deploy prep
  Ensure partial sync trigger is subscribed during synchronization, unset said flag on completion
  Un-break services that aren't Garmin Connect
  Polling worker & scheduler
  Cache GC cookies by email too, not just service records
  Well, at least I didn't commit pdb.set_trace()... Still laughing though.
  GC partial sync triggering logic
  Rearranged service_base, added polling infrastructure
  Fixed potential weirdness resulting from modifying activity list during iteration for deferred services.
  Cherry-pick partial sync trigger stuff from endomondo-2