Updating custom color output

Resolves #410

Adds two new Appearance settings for **interaction** colors that can be specified and then used for hover/active color change effects on button color. 

Took this opportunity to clean up the **SettingsController** and *DRY* up the repeated functions so it's easier to update controller and those functions moving forward. Also added some new custom color style output logic to output the custom color options more responsibly.

@angaither 

CC: @barryclark @DFurnes