Phalanx selection mechanic tweak

- When in edit mode, if you click on a piece that is not part of your
current phalanx, instead of not adding it to current phalanx, it
switches your current phalanx to the piece you clicked.
Phalanx selection tweak

- You cannot unselect all pieces in phalanx mode
- This fixes the problem the used to exist, namely double clicking a
single piece will go into edit mode but unselect the piece you clicked.