fixes #221 thumbnail images for external projects are now loadded from main project/public_html/images/all_challenges/ instead of external server
fixes #221 Moved projects xls filename and location of thumb images to settings file
Fixes #276, full url in submissions link is now rendered properly, without prepending project url.
In projects overview data download url can now differ from general url. Also added basic testing for all_projects template tag: Testing whether rendering it renders any html does not crash page
Merge branch 'dev'
git status
Finalized external project submission form. Added in tests as well