Add experimental darkplaces quake

Just darkplaces-rpi with shareware game file from id software. Runs nice if you run RetroPie/roms/ports/darkplacesquake.sh from console.  If it is run from emulationstation there are issues. Controls are different and the menu cannot be used. I don't know why, but there seems to be a problem between emulationstation2 and SDL/SDL2 games/emulators like mupen64plus-rpi and darkplaces quake.

Workaround: Run dark places as root atm (line 44).