Caylus UI: Include placement cost of worker in instructions

[Xelvonar]

A small and probably easy to implement suggestion: When it is your turn to place a worker, include the default cost to place a worker in the text notification at the top of the screen. Ex: "It is your turn to place a worker (default cost: 2 Denier)." I've often placed a worker without checking the cost and ended up messing up my turn.