radicale: Expose inbuilt web interface

Radicale 2.x comes with its own web interface creating, deleting calendars. Depending on the client they are using, users don't always have the ability to manage calendars from client. It would be nice to expose the inbuilt Radicle web interface for managing calendars.

Primary issue seems to be that Radicale comes with its own authentication mechanism and may not recognize Apache's provided REMOTE_USER (that we currently use).

• Investigate and fix this issue.
• Add to client information about how to reach this web interface.
• Update manual.