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
fix startup NPE
hide zoom buttons when opening metrics sidebar
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
Merge branch 'dev' of https://github.com/garvankeeley/MozStumbler into acra-npe-mapfragment-scanner-hasnext