Switch to using Ancaa in Companion Chess

Switch to using Ancaa in Companion Chess

Now we can do bent riders, the Ancaa is a better Queen replacement
as the Adjutant, as it does not need an unnatural color-switching move.
Also there is no reason that the same piece should be used for castling
K-side and Q-side, so we replace one of the corner pieces by a
'sliding Gnu', for which the C move can be blocked on the N square.
Leave a pure (color-bound) Adjutant in aspromotion choice, to play with.