This patch is based on Caolán's one at 68075a61
I've chosen the background color used in Windows program Paint.NET as
our default background color. It's a nice compromise that doesn't look
out of place anywhere.

Change-Id: I5081201043be4a7ad6152d1ce59451daa4ece1ac
Reviewed-on: https://gerrit.libreoffice.org/10527Reviewed-by: Stefan Knorr <heinzlesspam@gmail.com>
Reviewed-by: Christian Lohmaier <lohmaier+LibreOffice@googlemail.com>
Tested-by: Christian Lohmaier <lohmaier+LibreOffice@googlemail.com>
Reviewed-on: https://gerrit.libreoffice.org/10520Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>