Bug 1030249 - server purge pending commands on disable

* remove ALL pending commands when a device reports it's disabled.
* use long commands for debugging & errors
* correct "device" to standard "deviceId" in logs
Update default for fxa.login_url to include uid
Merge branch 'dev' of github.com:mozilla-services/FindMyDevice into dev
Correct for golang's header normalization

* Use Header.Get() rather than index directly.
* move push defer after error check because otherwise exception
Merge pull request #256 from jrconlin/dev

Bug 1030249