Streamlined startup configuration a bit. Collection is the starting profile...

Streamlined startup configuration a bit. Collection is the starting profile and the startup directory is found this way. The ipython startup script now uses parse_yml to parse a devices.yml file to get dicts of names and URIs of devices. If the environment variable COMMUNICATION_LAYER is 'epics' it will automatically create motor devices. This is done as an example. Tango will be done in another branch what uses the tango development branch of ophyd_async.