Replaced old and busted icon design, with Google's generic app icon.
It is now a vector drawable, which means it will be sharp at any resolution,
while we only need to keep one tiny xml file for it. No folder thumbnail
support, but this a welcomed change nontheless.

Change-Id: Ie6e38a6ac8e6cf1bc2d22247c11b5de0bd0d8478
Reviewed-on: https://gerrit.libreoffice.org/32498Reviewed-by: jan iversen <jani@documentfoundation.org>
Tested-by: jan iversen <jani@documentfoundation.org>