Better Traceback/StackTrace

[awilliamson]

Traceback returns a string, it's horrible, and only so much we can display from a single string.
I found the following:
https://github.com/ignacio/StackTracePlus

which provides a much nicer stack trace, and also advanced options such as adding known functions etc, which could be useful for SF-space erroring in the future.

The only thing which we can't implement is the io, everything else should be runnable. As we're using 5.1, this will work as we can't call the new 5.2/5.3 version of traceback ( which is stated as being hard to override as it's internal ).

Thoughts?