Implement a connector plugin that is capable of reading and writing
messages from and to the standard input/output.

This connector will print each message to the standard output, with
each message appearing on a new line. If Connector::ID is supplied
it will be prepended to the message in format _"<id>: <msg>\n"_.

The std_connector can also read messages from the standard input,
using the newline character as the delimiter.

The configuration of the std_connector Connector results in the creation
of a single ConnectorCommon object. This object is responsible for holding
a list of all the Connectors being configured. Within the ConnectorCommon
object, there is a vector<> that stores individual Connector config objects.
The ConnectorManager then uses this vector<> to instantiate the desired set
of Connectors.

std_connector pre-configures 3 default connectors:
* stdout: default transmit connector
* stdin: default receive connector
* stdio: default duplex connector