Create 00_special_troops.txt

There was no 00_special_troops.txt, so PB was just using the vanilla special unit definitions, and didn't have the increased maintenance for camel cavalry or horse archers. Problem solved!
Delete 00_special_troops.txt
Create 00_special_troops.txt
Create 00_special_troops.txt
Merge pull request #178 from bnormoyle/beta

Beta
Merge pull request #179 from zijistark/alpha

defines.lua compatibility with beta patch 2.1.5.6
Catholic crusades after catholics mend schism

Adding the check for cath_schism_mended to the crusade CB
Merge pull request #180 from bnormoyle/patch-2

Catholic crusades after catholics mend schism
Less Papal Investiture nagging
Reduced knights maintenance

Also got rid of increased special troops maintenance
2.1.5.6 on_actions compatibility update