Allow desktop development using docker services

[sddj]

This change set is for enabling MineMeld (minemeld-core and
minemeld-webui to be debugged on the desktop using docker to run the
required services, PyCharm for editing and debugging minemeld-core,
and WebStorm for editing and debugging minemeld-webui. To accomplish
this, changes are required to be able to configure remote connections
to the services as they appear remote when running in the docker
containers.

• The minemeld/cli files are used for creating debug targets in
  PyCharm. These guarantee that GEvent monkey patching is performed
  before loading other files.

• The collectd path can be prefixed with tcp://, in which case a
  remote connection to collectd will be created. Otherwise, a UNIX
  socket at the specified path is created.

• The zmqredis file was modified to centralize the creation of the
  path to connect or bind to, reducing the number of times
  'ipc:///var/run/minemeld/' is hardcoded into the file and
  standardizing the interpretation of '@' at the beginning of the
  path. It should also be possible to use TCP as the ZMQ transport
  using tcp:// as the configured path, though this has not been
  attempted.

• Since minemeld-core is being run not as an installed package, it was
  necessary to introduce 'initialize_default_nodes_distribution()' to
  load nodes from the json file at startup so that the node prototypes
  can be found.

• Configuration, such as the redis URL, is looked up from
  configuration using a 'get_config_value()' convenience function
  which loads from this path until the value is found:

  1. config (e.g MGMTBUS.config.redis_url)
  2. os.environ (e.g. MGMTBUS_CONFIG_REDIS_URL)
  3. the provided default value

See https://github.com/sddj/minemeld-docker for the required base
files and setup instructions.