Only display the "Center Me" button when the view is not centered

There's no need to have the button there obscuring the map when it would have
no effect to press it.
Update Marathi translation
Update Hindi translation
Further cleanup. Create isSupported() check on the cell scanner
implementation to see if it usable. The wraps up some repeated checks
the code was doing.
Merge pull request #1221 from cascheberg/fix-metrics

@cascheberg Show unique number of networks in metrics
Merge pull request #1237 from garvankeeley/cellscanner-move-null-check

Additional cleanup: Create isSupported() check on the cell scanner implementation
fix startup NPE
Merge pull request #1239 from cascheberg/fix

Fix NPE startup crash
Merge pull request #1231 from keverets/hide-centerme-button

Only display the "Center Me" button when the view is not centered
Merge pull request #1241 from cascheberg/fix-metrics

@cascheberg Hide map zoom buttons when opening metrics sidebar
Merge pull request #1235 from vinitraje/dev

@vinitraje Update Hindi & Marathi translations
Added global makeLogTag function to ensure tags are 23 characters or
less. Android has a soft limit on this of 23 characters, and depending
on the logging function used, it may or may not enforce this limit.
onDestroy, cancel the alarm
Change isSupported -> isSupportedOnThisDevice, and make
isSupportedOnThisDevice use the existing mTelephonyManager if available.
Merge pull request #1243 from garvankeeley/cellscanner-move-null-check

Sync Fennec code with stumbler github