Add search metric

[norgeindian]

It would be great to know if the catalogsearch works as expected.
So a metric could be added, which checks for the amount of searches and the amount of the corresponding results.

[sprankhub]

Could you add some details how you think this could look like? Would the merchant define search terms and a minimum amount of expected results? As in: If I search for X, I expect at least 10 results.