add new map Hopes Anchor by @NukemBro

http://resource.openra.net/maps/1368/
remove maps

closes #5458
added Oasis Conquest

http://resource.openra.net/maps/1470
added Desert Twister by @psydev

http://resource.openra.net/maps/990
added Vladimir's Folly

http://resource.openra.net/maps/1639/
Fix the --png utility command. Closes #6845.
Merge pull request #6841 from Mailaender/hopes-anchor

Added a new map Hopes Anchor
Merge pull request #6844 from Mailaender/new-d2k-maps

Added new maps to the Dune 2000 mod
Merge pull request #6847 from pchote/fix-utility

Fix the --png utility command.
remove Convergence and River War maps
Merge pull request #6842 from Mailaender/map-scrap

Removed several maps from the Red Alert mod
remove map Brimstone
remove Year 501

closes #6447