WelcomeScreen: Changing the "Getting Started Now" button url

We want to reduce the needed number of clicks to the Android setup
info from 4 to 2 clicks. Therefore the main index.html i better.
Also that page does not open in split help, anymore.

Change-Id: I96b43f269c946c3a836811480ee29221db5fade9
Reviewed-by: Sami Makkonen <sami.makkonen@digia.com>
Reviewed-by: Alessandro Portale <alessandro.portale@digia.com>