decide which mirror to choose locally and display result

closes #3904
Make the ready overlay blink. Fixes #3032.
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.
Issue #4650: Abort Mission Confirmation

Adapted the confirmation dialog from the CnC mod and wired it to
the "Abort" and "Surrender" buttons.
Updated & renamed no_escapism. added trees.
renamed skull valley. now 4p. bridges fixed.
Adding "pressure" map.
Merge pull request #5178 from pchote/get-blinkin-ready

Make the ready overlay blink.
Add confirmation-dialogs.yaml to d2k's and ts's mod.yaml or they crash
Hide ingame menu before showing the confirmation dialog

As a bonus, don't show the confirmation dialog if the game is over.
Update license headers
Merge pull request #5180 from pavlos256/abort-mission-confirmation

Closes #4650
Make Stopwatch.ElapsedTime() a property and TimeSpan
Repurpose unused Timer.cs and add some loading perf metrics
Improve PerfTimer output