License-add and change args Gstate.next_move
Moving handling of rules into Control module
Simplified board-movement function and made it match design of Control module better
Added Control module game-logic skeleton for non-existing Rules-module functions - to be implemented next.
Moved element-costs from Rules into gstate
Minor rename and type gstate addition
minor: added element-cost initialization
Rewritten simple rules-functions to read cost from gstate