X-Men hero cleanup

[SwedeRacer]

I've identified a few minor issues that can be cleaned up in the four new X-Men heroes:

• The scales of generated cards are not being set. There are new constants in the global file that can be used to scale the various card types.
• Obligation cards are being placed face-up; they should be face-down to go in the encounter deck.
• Playmat image files are too big. The playmat images are around 30MB, and they take a noticeably long time to load. We can reduce their resolution and compress them to make them much smaller.
• Hover text of selector tiles includes unnecessary "Hero". For instance, "Cyclops Hero". I'd been using a naming convention for the hero bags and getting the hero name from this, though I wanted to move the name into the HeroDetails. Since we're moving away from bags this will be the way to go anyway.

[funkymonkeymonk]

• The scales of generated cards are not being set. There are new constants in the global file that can be used to scale the various card types.
• Obligation cards are being placed face-up; they should be face-down to go in the encounter deck.

Fixed in #63