make Volkov a true Cyborg

- Added new Armor value: Cybernetic
- Use sounds/graphics from DE censored version
- Heals near repair pad (instead of hospital)
- Medic can't heal him
- Dogs can't eat him
- Tanks need to attempts to crush him
- +25% HP (now same factor as 4tnk:1tnk compared to e1)
add @Generalcamo to AUTHORS

original Volkov contribution came from
http://content.open-ra.org/index.php?p=detail&table=units&id=132
Introducing per-player shrouds.

- Each player has their own shroud and their visibility does not extend outside of the shroud. 
- Units and buildings can no longer target other units outside of their visibility. Buildings can still be targetted if they have been explored.
- GPS will provide visibility in the fog-of-war.
- Spies that infiltrate radar domes will gain their victim's exploration and reset it on all clients (if the victim does not have GPS)
Three new 5-player RA maps:

- The White Pentagon - snow based land/water map with minimal obstructions.
- Black Gold - Resource starved map with each starting position receiving 8 oil derricks.
- Texas Sea - Similar to Black Gold, but every starting position is on a tiny island.
Merge pull request #2509 from Lookingglass/lg-maps

Three new 5-player RA maps
Merge pull request #2498 from Mailaender/volkov

make Volkov a true Cyborg
Adding Shroud trait to CNC / D2K mods
Fixed airfield name.

The name of the airfield was airstrip... which is wrong since the icon says airfield whilte the building is called airstrip... its even called AFLD in the code so... just a simple fix :)
don't hardcode custom prerequisites anymore

to make those strings translatable
expose strings from build palette widget to chrome yaml

prepare for localisation efforts
customisable text printed on RA support power icons
customisable Ready/Hold text for CnC mod

make those strings also translatable
Merge pull request #2524 from hunnybunny95/patch-1

Fixed airfield name.
Merge pull request #2525 from Mailaender/custom-tech

don't hardcode custom prerequisites anymore
Merge pull request #2526 from Mailaender/strings

made all in-game strings customisable via .yaml files
Merge pull request #2507 from Lookingglass/per-player-shrouds

Per-player shrouds
Fixed repairing landed airplanes (most likely #2365)

When an airplane was landed and ordered to another airstrip or service depot, the aproach distance was not properly calculated since it was not taken into effect that its current altitude is zero.
Changed scroll velocity in the map chooser to be better suited for mouse scrolling
Added RA map: ghost town
update CHANGELOG