Node::local_path() function is not good enough

[Peter Johansson]

Instead we would need something like

/// \return output directory relative to Parameter::target()
std::string outputdir(string user, const line_type) const

/// \return output file relative to Parameter::target()
std::string outputfile(string user, const line_type) const

These, and perhaps some more, function should be used in generation of output to make this code more readable.

[Peter Johansson]

(In [252]) fixes #168, the if statement introduced should be built-in to a function refs #169