Adds option to disable upnp listener

[jlippold]

This is needed so the echo does not discover devices when you don't tell it to. If the upnp listener is always on, then the echo refreshes the device list without your approval.

This is also useful if you want to run multiple ha-bridges on one server, like:

java -jar C:\dir1\amazon-echo-bridge-0.2.1.jar --upnp.config.address=192.168.1.110 --server.port=8080 --upnp.response.port=50000 --upnp.disable=true

java -jar C:\dir2\amazon-echo-bridge-0.2.1.jar --upnp.config.address=192.168.1.110 --server.port=8081 --upnp.response.port=50001 --upnp.disable=true