Add campaign support for ferry-only bases.

[DanAlbert]

Fixes #3170.

[codecov]

Codecov Report

Merging #3173 (078161c) into develop (e43874e) will increase coverage by 0.00%.
The diff coverage is 42.85%.

@@           Coverage Diff            @@
##           develop    #3173   +/-   ##
========================================
  Coverage    45.77%   45.78%           
========================================
  Files          472      474    +2     
  Lines        25741    25793   +52     
  Branches      4508     4515    +7     
========================================
+ Hits         11783    11809   +26     
- Misses       13937    13963   +26     
  Partials        21       21           

Files Changed	Coverage Δ
game/squadrons/airwing.py	31.52% <0.00%> (-1.44%)	⬇️
game/version.py	68.18% <ø> (ø)
game/campaignloader/controlpointbuilder.py	31.57% <31.57%> (ø)
game/campaignloader/mizcampaignloader.py	35.91% <36.36%> (+0.74%)	⬆️
game/campaignloader/campaign.py	50.84% <50.00%> (+0.42%)	⬆️
game/campaignloader/controlpointconfig.py	85.71% <85.71%> (ø)
game/theater/controlpoint.py	49.77% <100.00%> (+0.05%)	⬆️