Reducing log spam, need to review with @crankcoder to see if any of
these need keeping
Merge branch 'dev' of https://github.com/mozilla/MozStumbler into less-log-spam

Conflicts:
	android/src/main/java/org/mozilla/osmdroid/tileprovider/modules/TileDownloaderDelegate.java
Coverage url was accidentally made non static in a previous change. The
means it gets re-inited more often, and more logging errors if there is
no network. Also wrapped the logging for this in debug-only.
Spamming log with "tileURLString is empty or null" when the tile source
is set to blank, which is a required state for low res tiles.
Merge branch 'less-log-spam' of github.com:garvankeeley/MozStumbler into less-log-spam
Merge pull request #1126 from crankycoder/less-log-spam

Supercedes #1118