This patch moves:
* `kush_cavalry_javelinist_merc*` → `blemmye_camel_javelinist*`
* `kush_infantry_javelinist_merc*` → `nuba_infantry_javelinist*`
* `kush_infantry_clubman*` → `nuba_infantry_clubman*`
and updates all files that use them accordingly.
As a result, any player that captures a Blemmy camp or Nuba village can train these mercenaries there (but only Kushites can build these mercenary structures).