Settings: Slimrecents card/text color [1/2]

Allows user to set custom colors for Slimrecents card
    header text and background.

PS: fix strings

PS: move recent preferences into separate
        subcategory under Interface settings (squashed).
Change-Id: I6cd62c14f0d2b1aba54efa7dfa0c8a3db7669a9e