Added a ^BaseBuilding default that Inherits ^Building to CnC mod.
Moved some traits, including MustBeDestroyed, from ^Building to ^BaseBuilding.

Removed some now superflous traits and trait negations from ^CivBuilding.

Changed Inheritances of all buildable structures to ^BaseBuilding.
Merge pull request #5146 from reaperrr/mbd-fix

Removed MustBeDestroyed from CnC Civ/Tech buildings