[scribus] Scribus Image (Resource) Manager

[Peter Nermander]

> i think that we can safely keep the different types of resources
> separated...

I was thinking the same.

Images are external resources referred to by the Scribus document so
managing them with a separate dialog makes sense (Manage images was
created based on a need).

Fonts have a dialog in the setup and also in PDF export. Maybe there
should be some kind of merging between them. If a font is set as
"Don't embed" in the setup that setting can currently not be changed
from the PDF export dialog.

/Peter