Show mana upkeep on card #150
Description
We need to show the mana upkeep value on the card, if the card has such a value. This is a significance in particular for Mythos because many cards have an upkeep as well as a casting cost. This should be fairly simple to add in the CardModel on the existing mana button, to display say "💧15 / 5" for a card with 15 cost and 5 upkeep, and "💧15" if the card has cost but no upkeep.