indicate dependencies' Python3 support in requirements.txt
sort entities in natural (not ASCII) order

collections,entities,files lists in DDR.models are already
in natural order.
nav: "Web UI" > "Collections"; mv Storage link in nav
install.sh: specify target dir for wget,7z; assume yes for 7z x

Instead of cd-ing into directories, specify the wget,7z target.
Assume user wants 7z to overwrite files.
install.sh: Use vars for bootstrap,modernizr,jquery versions
hide edit buttons if user not logged in
make file-detail visible to anonymous users
Merge branch 'master' into 092-public-site-medusa