Ease of understanding metrics

[robpalme]

The four classes of metric for assessing completion are not easy to understand unless you go to the website and read the definition. Especially in tweet form for newcomers.

• Required means a true negative, which is a type error that is not reported by stc.
• Matched means a true positive, which is a type error that is reported by stc and correct.
• Extra means a false positive. In other words, it's the number of incorrect errors stc emits while it should not.
• Panic means the analyzer panicked while validating input files, due to a logic bug.

It's hard to know which of those numbers you want to go up or down. So in string form I suggest ordering and calling them:

1. matched (was matched)
2. bad_missed (was required)
3. bad_excess (was extra)
4. bad_panic (was panic)

[kdy1]

I'll use those words starting from the next update. Thank you!