Increase the boost for prefix matches.

This is a fix for #3411 and is going to be useful for code hinting
Make numConsecutive actually mean what it says.

In the process, I tweaked the bonuses to keep things ordered well.
Extract consecutive boost value to variable.

Per review feedback
Merge pull request #3493 from adobe/dangoor/3411-prefix-match

Increase the boost for contiguous matches that make up a prefix