Add function to test gap analysis

[gavinbaumanis]

Summary

Assuming your test spec's name contains the function name:
Perform a gap-analysis of functions that do / do not have a test.

Detailed Description

Provide a list of your application's function names that do not have a matching test spec.

[lmajano]

I think this should be part of the TestBox cli right?

[gavinbaumanis]

I don't have a strong thought either way.
I added it to testbox html runner - because then it can be "seen" what it is doing a little more visually - and how it is different from a normal test run.

But there is no reason at all - that it can't be in the cli.