Error handling and traceability improvements checkpoint.

[digimaun]

• ResolverClient supports optionally passing in an ILogger
• Uniform resolution exception ResolverException which aggregates inner exceptions (httpexception, filenotfound exception, directorynotfoundexception, etc).
• More clear error descriptions.
• Tests to support updates.
• CLI supports --output / -o for writing result content to file. This has the advantage over redirect to keep verbose logging on, while preserving only the model content to write to file.