Bundlebuilder - accept repository for AppStream metadata
Bundlebuilder - accept repository for AppStream metadata

AppStream metadata generator was looking for key repository_url, but
Wiki and common usage has adopted repository.

sugarlabs/sugar-toolkit-gtk3,quozl/sugar-toolkit-gtk3,sugarlabs/sugar-toolkit-gtk3,quozl/sugar-toolkit-gtk3,sugarlabs/sugar-toolkit-gtk3,quozl/sugar-toolkit-gtk3,quozl/sugar-toolkit-gtk3