WIP: Add option to ignore exceptions

[automata]

Shows exceptions, dump a trace but do not exit process if option is true. As suggested.

I should add that on other PR, too late. Sorry.

[jonnor]

@automata I don't think this specificially needs an automated test. Just run with & without the --ignore-exceptions option and verify it does the right thing.

But if you'd like to add something for the exception catching, can do that in https://github.com/noflo/noflo-runtime-msgflo/blob/master/spec/tracing.coffee - need to add some NoFo component + graph which allows to cause exception.

[automata]

@jonnor added a simple test, can be extended to other options as well. Just saw your comment now, can remove the test by rebase if needed.

[jonnor]

Parse test is fine, though generally I don't care much for unit tests. But if you're gonna have that, at least also have a test for when option does not exist.

[automata]

Right, gonna go deep in this hole later. Do not merge, please. Back into debugging caliper now.