Rename options to be consistent with other TwentyXX themes. Move Featured Content settings to 2014 Featured Content Group.

Rename groups to be consistent with Styles TwentyXXX plugins and WordPress nomenclature.

Rename control labels

* Remove redundant "Widget" inside widget group, "Featured" inside featured group, etc.
* Remove redundant "BG" — Styles adds "Background color" next to the label
* Change "a:before" to non-technical "Before Link"

Append 'Featured Content' options to append to 2014's default 'Featured Content' group

Warning: These changes will cause settings to not carry across upgrade if a migration script isn't written.