Add sack button to soldier info screen

Currently a player must look at a soldier's stats, decide a sacking is
in order, click ok, click ok, click sell/sack, forget the name of the
soldier, go back to the soldier's list, back to sack/sell, can't find
the soldier, more clicks, remove soldier from craft, yet more clicks,
finally sack the soldier.
This extra button might lessen player stress.