Retrieve running MetroProcessor instances via Karabo WebProxy
This MR replaces the static known_metropc_output.txt file with retrieval via known webProxy devices. I will add a refresh button to the GUI later to get a new list without restarting.
Also adds a topic argument to extra-metro to make the list shorter, e.g. extra-metro SQS. Otherwise the $SASE environment variable is used to narrow down the number of possible topics.