Bug 25741 - TBA: Add mozconfig for Android and pertinent branding files.

Based on Orfox initial commits with fixup commits squashed and
rebranding Orfox -> Tor Browser

See original source from ce3fab3c90eb4a3892181ee36b037da04c785d99
https://github.com/guardianproject/tor-browser.git

Dropped symlinks

Also:
Bug 27125 - Move localized Tor Browser for Android strings into separate file
Bug 28622: Update Tor Browser icon for mobile
Bug 27472 - Export MOZILLA_OFFICIAL during Android build
Bug 30136: Use 'Tor Browser' as brand name on mobile, too

Bug 27111: Configure tor browser for mobile to load about:tor

- Add preferences.json: it is used to configure android specific
preferences

- Keep the ActivityStream HomePager closed when the user clicks in the
url bar