Goodbye classic mods

The community around http://cnc-comm.com/ and http://cncnet.org/ is hostile. No one cared for the classic mods. They are also redundant and waste developer time, mostly @pchote during his refactors to add Tiberian Sun support.

* Created https://github.com/OpenRA/OpenRA/wiki/FAQ#this-is-not-true-to-the-original which will redirect them to the more popular http://redalert1.com site.
* Will send deletion request for http://www.moddb.com/mods/openra-classic
* Just closed our TODO list at #2740 and will do the same with all related feature requests.

You can still send a patch if you want to maintain it again. Probably also remove all the redundancy in the yaml rules and inherit more from the ra/cnc mods to succeed.