Use default values everywhere so they don't need to be specified in the
.env file.
This makes the default .env file much smaller (the larger config options
are documented in the handbook) and should make it easier to port the
setup to runtimes other than Docker Compose.
* jicofo: add optional XMPP_PORT value
* include compose and env example for XMPP_PORT
* extends use of the XMPP_PORT property
* fix compose to use default
* re-commenting XMPP_PORT value
* include XMPP_PORT in compose for all services
* always use $XMPP_PORT, value defaulted in template
* missing JVB setting
