DCUO Power Sets v2

In context, a few icons from the original shot didn't work.

- Light (Villain) didn't have enough contrast, so that was improved.
- Nature was too complex, so it was simplified.
- Light (Hero) was too bright, so it was toned down.
- Gadgets was too complex, so it was simplified.
- Celestial (Villain) was too dark to fit in with the other icons, so it was lightened slightly.

Finally, I needed an icon for a blank state, so an "unknown" power icon was added.