Fail gracefullier
Improve tests for utilities
URLCache now has callback on resource
Add Observation Maps feature
Update tests to cover observation layer
Properly display "issued at" times using pytz to determine timezone
factoring.

Note currently assumes TZ of Europe/London until I figure out how to
pull a proper value from XBMC.
Cached items have expiry based on UTC times
Fix issuedat times in observation map tests