build palette hotkeys require ALT modifier to avoid conflicts

changed back the unit action hotkeys scatter / stance cycle
Remove leftovers from moving cheats into options menu.
shortened MSAM name. Tweak cloak time

Mobile SAM launcher name shortened. 
Stealth tank time increased 80 -> 90 until https://github.com/OpenRA/OpenRA/issues/2898 is addressed.
Shortened a few other names.
Fixed some descriptions.
Break production tabs logic into a separate file.

Also unhardcodes the production types.
Remove duplication between ButtonWidget and ToggleButtonWidget.
Merge tooltip support into Button and remove ToggleButton.
Use IsHighlighted for settings / ingame menu tabs.
apc gun given recoil
APC muzzle flash made single shot inst. of double
set A.I. max silos to build == 1, to save space

Due to conyard build radius, unnecessary buildings should not be built.
Silo is not really needed, so capping to 1. 
updated skull_valley. Fixes, and now 8-players
Merge pull request #3008 from pchote/split-tabs-logic

Split multiple-production-queue widget logic into its own file
Merge pull request #3010 from psydev/bleed

updated skull_valley: fixes + now 8-players
Merge pull request #3007 from psydev/patch-1

shortened MSAM name. Tweak cloak time. Fixed desc's.
fix empty camo pillboxes in shellmap
allow the cloak palette to stay empty and use it for mines
Merge pull request #3009 from ScottNZ/mtm-shroud

Fixes a couple of shroud issues
Merge pull request #3011 from Mailaender/cloaking

Render mines properly again and fix empty camo pillboxes in RA shellmap
Merge pull request #3003 from Mailaender/build-palette-hotkey-modifier

Resolve hotkey conflicts between build palette and world command widget once and for all
Add Desert Shellmap