building up

running api/core tests from checked-in fixtures instead of live/remote data
added fixtures for git-api/raw data
moved cached loading to own classes
* extracted cached-loading from git api/raw
* created xm.CachedLoader et al
* added storage services for json and flat text
* added cache-skip options to loader
* unified cached loading in git-api and git-raw
added StatCounter assertion to helper
various small edits