Tweaked the openSUSE build service links

This adds links to the openSUSE wiki with further information
* https://en.opensuse.org/OpenRA
* https://en.opensuse.org/Games

and avoids linking the download page twice. Also it may be confusing that you don't get a package, but another HTML site with instructions. I tried to mitigate that by renaming the button a bit.
Hmm, if you want the download button to just work, then the problem with one-click-install is that we need to link all repositories:
* http://software.opensuse.org/ymp/games/openSUSE_Tumbleweed/openra.ymp
* http://software.opensuse.org/ymp/games/openSUSE_Factory/openra.ymp
* http://software.opensuse.org/ymp/games/openSUSE_13.2/openra.ymp
* http://software.opensuse.org/ymp/games/openSUSE_13.1/openra.ymp
* http://software.opensuse.org/ymp/games/openSUSE_12.3/openra.ymp