added the ability to recieve a eieio message (just a basic packet, if we need command packets then ill revisit this).

required a supported method in eieio-header

This is not tested as requires sergios live packet gather to be able to transmit packets first
Merge remote-tracking branch 'origin/spinnman_register_listener_branch' into spinnman_register_listener_branch

Conflicts:
	spinnman/messages/eieio/eieio_header.py
removed a floating thing