cleaner style in web UI
add metallic theme to web UI
fix collection list in web UI
create default collection in demo store
merge newer metallic web UI

Merge branch 'develop' into feature/irods

why this merge is necessary,
further web UI styling
added custom authentication

Added custom Authenticator to check credentials and handle
On-Behalf-Of requests.
add On-Behalf-Of header in client

Scrape local client user's username from os.environ['USER']
create only one collection by default - `default`!
merge latest UI and non-iRODS specific changes

Merge branch 'develop' into feature/irods
fix config base URL for actual demo server
for demo purposes, accept all On-Behalf-Of requests