decide which mirror to choose locally and display result

closes #3904
Fixed #3826
Update structures.yaml

Removed CanPowerDown trait
Add a camera to the Ion Cannon. Fixes #5058.
update to GeoIP2 and parse the database only once

closes #4227
Merge pull request #4666 from Mailaender/geoip2

Updated to GeoIP2
Make nuke flight time independent from map size.
Add a camera to the nuke.
Change D2K airstrike shroud reveal to match TD.
Support indefinite beacon duration for support powers that remove the beacon on completion.
Persist the nuke beacon until detonation.
Fix GDI03 airstrike power.
Update changelog.
Merge pull request #5066 from pchote/weapon-cameras

Superweapon tweaks
fixed Reference is expected Line 89 position 6
Mods.RA also requires MaxMind.GeoIP2
Merge pull request #5129 from Mailaender/csproj-reference-xml-error

Fixed Reference is expected Line 89 position 6
Nerfing guard towers

Range of obelisk, Adv. Guard Tower and SAM site reduced.
Damage of Guard Tower reduced vs. infantry and light vehicles; spread increased to compensate a bit.
Damage of Advanced Guard Tower nerfed, especially against light vehicles. Damage vs. infantry increased (though it's still low DPS). Spread also increased to compensate for its lack of power vs. infantry.
Turret damage mostly unchanged, but does less damage per shot. Damage vs. light vehicles increased to match damage vs. heavy armor. Damage vs. infantry slightly reduced.
Improve Hum-vee/Buggy machine gun vs. infantry

Hum-vee/buggy machinegun buffed to make them more useful vs. infantry. Currently they are rather weak. 
Damage vs. other types of armor reduced to compensate.
Flame Tank damage vs. light increased