Fix TechTree prerequisite bug for buildings with a build limit.

Fixes where a building/unit whose prereq is a build limited structure
was always available to be built even when the prereq was not satisfied.
Rewrite for better efficiency

uses a single, more concise statement rather than an if statement, and
checks buildLimit before attempting to check if the buildables cache
contains the key.
parse with NumberFormatInfo.InvariantInfo everywhere

closes #5240
fix trailing comma
remove unused OpenRA.Server extensions
StyleCop
New map: Year 501 (3vs3)
Updated hegemony_or_survival map.
More tiberium in middle, less in base.
New map: White Acres. 2vs2, FFA.
tiny fix to road for Dead in Motion redux
updated map credits for minus_two by petrenko
updated map credits for Llamas 2
updated map credits for Nullpeter by Petrenko
updated credits for dettering_democracy maps
renamed and updated credits for dead_in_motion_2
removed original dead_in_motion map
This map is a bit out of date, especially because of the build radius
which makes the starting positions a bit impractical. All the tiberium is
also in the middle, making this map a "rush for the middle". Since it's so
small, this limits gameplay considerably.
Dead_in_motion_2 addresses these issues and spreads the tiberium out a
bit, while also putting starting locations to one corner of the map. It
also adds blue tiberium.
I will add the old map on Resource.openra.net if anyone still wants to
play it.
New map: Letters_from_Lexington (1vs1)
New map: Pirates_and_Emperors (1vs1)
fixed map name of Year_501
fix template 84 (rock)