Handle rotation of JSON log files; change to daily, date-based rotation; Apparmor fix for static assets.

We were not managing the /etc/logrotate.d/nginx file, so
were relying on the package default. This wasn't aware of our *.json
log files. Oops!

Weekly rotation with delaycompress makes for some extreme disk space usage on any node with public traffic, so changed that do daily rotation, and allow for override of retention (default 365, to preserve existing default).

Changed to date-based archival, since this works better for both humans and - more importantly - backup/archival systems.

Squeezed in a fix to the apparmor profile to permit serving of static assets within configurable paths.