D8051: Enable custom background color to be enabled and changed from settings

[Luigi Toscano]

ltoscano added a comment.


  Can you please fix the summary so that it's not necessary to read the 
reviewboard entry?

REPOSITORY
  R223 Okular

REVISION DETAIL
  https://phabricator.kde.org/D8051

To: albertfreeman, #okular
Cc: ltoscano, ngraham, aacid