adding 'port' and 'comment' options to applicable junos_* modules

Adds the 'comment' option to the junos_install_config module allowing the user to supply a comment to the commit log if the commit was successful.

Adds the 'port' option to all the junos_* modules allowing the user to supply a non-default (i.e. other than 830) port for connecting to the device.

This last change is useful with SSH tunnelling and other port translation techniques. It is not intended to be used to support poor NETCONF implementations.