Enhancement: Show which rules match (in Preferences/Rules)

This is a small enhancement to CP that allows the users to explicitly see (in Preferences/Rules) which of their rules are currently matching and which are not.

Additionally, the changes made allowed an extra small performance improvement too: When the rules that match are exactly the same as during the previous check(s) -- and no changes to the rules or contexts have been made by the user, -- then it is not required to perform the whole re-calculation on the contexts and confidence levels as the result will be the same.

I would like to ask the team, those who can build from sources on their own, to try this enhancement on their systems.

Let me know if you like it and if you have any notes or comments from trying it in practice. Or from reviewing the related code.