Explain functionality for matching process

[mogronalol]

When there is no match, the response body will contain useful debugging information such as what matcher came the closest and which specific criteria it did not match on.

The problem is that we can also get the false positive scenario, where we are expecting a particular match to take place but a different one does instead.

We propose an explain functionality along the lines of hoverctl explain. This will take the last request made to Hoverfly, perform matching, and then output which criteria matched and what the score was for each matcher.

[JohnFDavenport]

This is a documentation issue