[1.4.8] Apply default accent colors to app icon(s)

Currently, it's possible to customize the app by choosing an accent color, but the app icon doesn't reflect this change.

Since many iOS apps today allow you to customize the app icon as well (and for color consistency), the app icon's gradient background or letter (depending on the icon style, of course) should change as well.

For example, if I choose purple as the accent color, I expect the displayed app icons to use that color as well.