radicale3: updates due to radicale 3 vs 2 changes

radicale3: updates due to radicale 3 vs 2 changes

* Various options have changed since radicale2, and the current
  initscripts set configuration that prevents radicale3 from starting
  in some cases. So update the options to radicale3.
* LuCI will not display the app when the config file is empty, so
  uncomment the first (server section) line.
* Changed the default data directory to /var (emphemeral storage) as
  OpenWrt policy is to not write flash by default. As with PostgreSQL,
  to be useful the user will need to set configuration for an
  appropriate path.

Signed-off-by: Daniel F. Dickinson <redacted>