2.04.0:minrog:6 Better Armies Purge

- removed a bunch of titles/characters/histories that were BA specific
- added event 7110045 - better_armies_mode (like hardcore_mode)
- merged BA mongol/SSI events into ck2+ base
- added Gallaway/Roman cultures to Castles
- merged BA retinue_subunits into ck2+ base
- moved BA localisation into ck2+ base