packagekit: Set the application description for long single line package descriptions
Don't show such a big gap on the details page if there are no screenshots
trivial: Support 'source' appstream entry types

This is used for improving the description of external repos.
trivial: New mockups show the details box for local packages again
Add 4 different infobars to show for local package types

For instance, we will soon show a warning when adding a repo, although this
is currently blocked on GetFilesLocal() and rh#1062703.