Updated the CommandDefinition to be able to handle getting the invoking endpoint ID and the invoking message ID.

references #28
Added the InvocationMessageAttribute which signifies that the parameter is the message ID of the invocation request message, and the InvokingEndpointAttribute which signifies that the parameter is the endpoint ID of the endpoint requesting the invocation.

references #28
Fixed issue with mixed up parameter order in the invocation array.

references #28
Updated example application with new ability to get command invoking endpoint ID from the system.

references #28
Merge pull request #28 from pvandervelde/issue/endpointidtocommand

Nuclei.Communication: Provide the sending endpoint ID to command invocations if required