Make gverify smarter if not all sigs match.

[TheBlueMatt]

eg find out which sigs do match and display the largest group of matching sigs as OK instead of checking each against the first.

[josephbisch]

How do we envision this working if there are multiple largest groups of matching sigs? Something like the following?

There are 2 largest groups of matching signatures consisting of 4 signatures each
Largest group of matching signatures #1
...
...
...
Largest group of matching signatures #2
...
...
...
The following 3 signatures are not part of any of the largest groups of matching signatures
...
...
...

Where the three ... indicate where the current formatting of gverify output would go.