Put in some more error checking, particularly trying to create connections
between layers/nodes that don't exist.

Write a simple net simulator with syntax loosely based on xerion. At
present this lot is API driven, it should be straightforward to write
a basic simulator that calls the API in the backend.

read & write methods for both networks and datasets modelled on snns format (for use with frontend script). data should be snns format, network definition file will probably have to differ

Implement an error method in addition to dbug, and clean up the dbug & error calls


