Pollute: converted attacks/powers have miscropped card images

[dbjorge]

As of #471, Pollute's implementation is pretty naive and doesn't do anything to try to correct attacks/powers' card images when they're converted to curses.

Options I can think of:

• Pollute adds some sort of extra inner frame image with a corrupted looking graphical effect that's big enough to cover the missing areas of power/attack images
• Patch AbstractCard.render* methods such that Polluted cards can still render portraits with the shape of the original card, but with the "Curse" text in place of "Attack"/"Power"/"Skill"