Refactor for services and messagebus to only be in a single file (the config file)

[craig8]

Instead of the following config file which is created now, where service-config is a separate file.

[volttron]
instance-name = WE48687
address = tcp://127.0.0.1:22916
agent-isolation-mode = False
message-bus = volttron.messagebus.zmq.ZmqMessageBus
agent-core = volttron.messagebus.zmq.ZmqCore
authentication-class = volttron.messagebus.zmq.ZmqAuthentication
authorization-class = volttron.messagebus.zmq.ZmqAuthorization
auth-service = volttron.services.auth
service-config = /home/os2204/.volttron/service_config.yml

The new config file will be as follows

[volttron]
instance-name = WE48687
address = tcp://127.0.0.1:22916
agent-isolation-mode = False

Assume volttron.messagebus.zmq if available.

Otherwise use the module to load.

message-bus = zmq

Services can be listed here identity = service path

[services]
platform.web = volttron.services.web
platform.auth = volttron.services.auth

[volttron.services.web]
bind-web-address = http://127.0.0.1:8080

Other services can be specified with key/value pairs for arguments that are passed through.