Redirect Special:Zero=>Main_Page if 'showZeroPage'

When user navigates to Special:ZeroRatedMobileAccess
(default landing page) for the carrier that has 'showZeroPage'
set to true, perform a redirect to the Main Page for zero|m
in the current language.

Change-Id: I101d1e12d2f3cf1195521f874ac0fc809b951a5e
Merge "Redirect Special:Zero=>Main_Page if 'showZeroPage'"