astakosclient: Add simplejson as recommended package

Astakosclient will fallback to Python's default 'json' package if
simplejson is not available. Still the use of 'simplejson' is
recommended since it is faster compared to the 'json' package.
debian: Add package support for snf-admin-app
Add vncauthproxy version dependency to cyclades
Add archipelago to pydist-overrides
Merge branch 'debian-release-0.16' into debian-develop