Fixed a bug preventing compatibility with Only Mod Civs

- Fixed a bug where, if Enlightenment Era is enabled, the EE-strength version of the Bausoldat could be built starting in the Medieval Era
- Fixed a bug where city-states could gift Bausoldaten (even if that's not the UU they're supposed to be able to gift)
- Fixed a bug where the description of the Berlin Wall decision would add a new "Righ click for more info on Berlin Wall" every time you moused over it until all of reality was nothing but right-clicking for more info on Berlin Wall
- In the process of fixing the second bug mentioned in this changelog, added a new bug where the civ select and load screens shows two Bausoldaten as uniques and ignores the Stasi, while the Civilopedia shows six Bausoldaten as UUs. This probably can't be fixed without reinstating bug #2, so given that it's a mere cosmetic problem, anyone who complains about it will be reported to the Ministry of State Security for counterrevolutionary activity