Make stomp.py optional #120
Description
Making argo-ams-library optional was done in #119, but making stomp.py optional is a fiddly task as stomp.py has a lot of low level integration in the code, which will need careful unpicking.
It may work to have a base Ssm2 class and then a class for each of AMS and STOMP that inherit from it such that only the STOMP one is a stomp.ConnectionListener.
Once done, this will hopefully enable pulling out AMS and STOMP functions to their own files/classes.