Fix server freeze on client absence.
Add WithRangeCircle trait for drawing arbitrary ranges.
Add proximity trigger plumbing.
Add UpgradeActorsNear trait for passive upgrades.
Add the stealth generator to TS.
Extend INotifyOtherProduction to all actors.
Apply upgrades to units produced within range immediately.
Fix spy tooltip definition.  Fixes #6665.
Fix TS offsets, selection bounds, weapon factory exits
Revert "build with latest Mono from @Xamarin"

This reverts commit f1bfbf933bb9cc170926233294f9ef9704cd3e7e.
Merge pull request #6672 from pchote/revert-mono

Revert "build with latest Mono from @Xamarin"
Merge pull request #6666 from pchote/fix-spy-tooltip

Fix spy tooltip definition.
Merge pull request #6644 from pchote/proximity-triggers

Closes #2175
Merge pull request #6546 from huwpascoe/freezefix

Closes #4591
Merge pull request #6663 from reaperrr/common-stuff4

Moved more stuff to Mods.Common
Fix Footprint, DockOffset, SpawnOffset and spawn Facing of TS refinery
Tweak TS barracks SpawnOffset and ExitCell
Merge pull request #6670 from reaperrr/ts-offsets01

Closes #5905
Mods.Common Effects

Moved over more effects to Mods.Common