Update app icon and launch images.

Switch to using an Asset Catalog for app icon and launch images.
Update Springboard appearance.

- Tweak standard background color.
- Set Springboard font explicitly to be bold. -boldSystemFontOfSize:12 isn’t that bold on iOS 7.
- Set status bar style to default: white text on black on iOS 6-, black text on iOS 7.
Update app version to 3.5.
Tweak app icon. Remove unused images.

- Make the bar of the i in MIT slightly more saturated.
Remove references to deleted images from xcodeproj.
Make the Links module look good on iOS 7.