Themes: Add method to "apply all" a theme

Change-Id: Ic8feaeade6c52707e6b5b17921b1b577b94ec8cf
Themes: Add URI for querying previews of applied components.

Change-Id: I97417901f3b03fc82df5a823970991ddd8092df2
Themes: Allow theming navbar bg color

Change-Id: I256afc30fc018ea752769029c5246bc7310c23a6