add variable to flag tank babies

The way that $activeSlave.origin is used to check for slaves raised in tanks just... upsets me. Having to do a massive string comparison is ugly, at best. Adds $activeSlave.tankBaby which will be 0 if not from tank, 1 if comforting conditioning, and 2 if terrifying conditioning. Also changes $activeSlave.origin for tank babies to be a little less verbose.