Code review comment for lp:~widelands-dev/widelands/rework-resource-indicators

Implemented most of your comments, and changed the graphics. Didn´t touch the atlantean images yet, will do so now.

I disagree about hardcoding the none-resi as "none". Hardcoded name restrictions are always a bad thing; it should be possible for a future modder to create a new resource named "none" if they want. Better not to have any hardcoded names and use the only string that makes no sense at all as a resource name, "".