Parse params into struct using Scan() before json.Unmarshal(), where possible.

Before this, json.Unmarshal() was used to scan param values into structs. Now where possible, Scan will be tried first because it does not required quotes in some cases and some cases not

E.g. when you pass in GET /test?a=1&b=2

And the params for A is a string and B is an int, the parser tries to json.Unmarshal with and without quotes to cater for both cases. That works fine, but when a Scan() method is available, we do not have to try both ways and have better chance of success.

Also changed the JSON order to try unquoted first then quoted, in cases where we still would do that.