cnc: Update cloaking, building destroyed sounds

- Use trans1.aud as the cloak sound, on both STNK and cloak
  given from crates

- Use crumble.aud rather than xplobig4.aud for building destruction
adhere to opendesktop menu-spec

Version= is the version of the .desktop file specification!
adhere to SPDX for RPM
increment debian copyright year
[CNC] Chinook priced reduced to $750

Halved Chinook price, $1500 to $750.
Infantry should be a more feasible strategy, and transporting them quickly will make them more usable.
This should be good for Nod especially since they don't have APCs.
Helipad reduced to $1000. Palette order fixed.

Helipad price reduced to $1000. Should make helicopter transports more accessible. Should also make having a few "support helis" flying around a more viable strategy, for non-standard builds.
Fixed palette order to be better grouped and in more progressive order. 
Re-arranged document so that it's sorted better.
use markdown for readme and contributing guidelines

- https://github.com/github/markup
- https://github.com/blog/1184-contributing-guidelines
Shroud creators now only temporarily block explored shroud.
On powerdown or removal from the game, any previously explored terrain will become visible once again.
Enabling mobile gap generators.