Metrics View UI changes: map legend
- removed this session cell and wifi count
- removed toggle for showing observation type
- added Map Legend section
bumped version to 0.40
* serialized the stack trace on error when using Log.e()
* added a Log.d level logger that does not emit output to the GuiLog.  Only info, warn and error will write to the gui log.
Changed Prefs::createGlobalInstance and ClientPrefs::createGlobalInstance to return the instance
write the mozilla api key into the prefs on MainApp creation.
Changed HTTPResponse to only write a Log.debug level message so that it does *not* go to the GUI log.
Made the log message AsyncUploader a little more explicit that this is the response from MLS Submission.
Merge pull request #945 from crankycoder/features/938-missing-api-key

Features/938 missing api key
Merge pull request #944 from garvankeeley/cleanup-metrics-ui-v2

Metrics View UI changes: map legend