decide which mirror to choose locally and display result

closes #3904
Updated Deterring Democracy map. Now 2p.
Updated Deterring Democracy Plus map
Updated map Dead_in_Motion_redux. Now 2p.
Updated Lessons From Kosovo map
Updated Manufacturing Consent map. Fewer start loc
Renamed slippery_slopes. Added blue tib markers.
Updated & renamed no_escapism. added trees.
renamed skull valley. now 4p. bridges fixed.
Adding "pressure" map.
Make Stopwatch.ElapsedTime() a property and TimeSpan
Repurpose unused Timer.cs and add some loading perf metrics
Improve PerfTimer output
Add more perf measurements
Optimize ComputeHash by removing Concat() and ToArray() calls
Fix OpenRA.Lint throwing because "perf" log channel does not exist

Slightly modified the Log class to allow dummy channels that don't
write anywhere, then use it on Lint because map loading writes to
the "perf" channel.
Prettier PerfTimer output
fixed tiberium tree in lessons_from_kosovo
balance tweak - make turret armor heavy

Since turrets have wood armor, they can get killed by flame tanks uber fast. It might be best if turrets are a counter to flame tanks, rather than their prey. If they have heavy armor, they will take far less damage, and not die instantly to a flame tank rush, making them able to contribute to some defense.
Style fixes