Improve card pool display, add control toggle

Made a bunch of changes here:
1) Cards in your pool now overlap to save space, hovering reveals the
whole card.
2) Sorting has been improved so that sorting by CMC sorts into columns,
ditto for rarity and color.
3) Added a show/hide toggle for the controls so that you can get them
out of the way if they are overlapping the cards you are looking at.
4) A bunch of minor CSS tweaks to make everything look a little bit
better.