ErrorPort implementation adapted to follow the pattern of others output
port implementations. Error port added to Collector and its usage
introduced at RunFlow. New output logged at output file.
Integration error, if no connection is specified at all for a port,
handled conceptionally in a flow design way forwarding a message over a
special port defined at FunctionUnit base class. All output and
error port traits extends FunctionUnit for handling integration errors
in that way.
Example for this handling implemented within Reverse and enabled at
RunFlow producing a different output including a stderr output.
Documentation corrected.
Overriding points for OutputPort name added used for integrration
errors. Example implementation for overriding added at function unit 
Normalize.
Documentation for output ports improved.
FunctionUnit companion object added enabling currying methods
allowing to register bunches of error and integration error
continuations in a convenient way, see RunFlow for examples.
Small documentation improvement at forwardIntegrationError.