add method for case-insensitive query parameter existence check

While according to RFC spec, query params are case-sensitive, there should be a method allowing for case-insensitive search for query params when just checking for existence.

var uri = "http://www.acme.com?test=1"
uri.hasQuery("TEST"); //returns false

New function signature would look like this:

URI.hasQueryParameter = function (data, name, caseSensitive) {
    //force undefined params
    var param3, param4;
    return URI.hasQuery(data, name, param3, param4, caseSensitive);
}

...with new param to main hasQuery method:

URI.hasQuery = function (data, name, value, withinArray, caseSensitive) {
// SNIP...
        switch (getType(value)) {
            case 'Undefined':
                // true if exists (but may be empty)
                return !caseSensitive ? name in data : return data[name] !== undefined;
// SNIP...
}
uri.hasQueryParameter("TEST", false); //returns true
uri.hasQueryParameter("TEST", true); //returns false

This approach maintains backwards compatibility without ugly calls from client script.

Start by locating the URI.hasQuery implementation and the existing query-parameter API described in the issue. Verify how existence checks currently handle undefined values, then make the requested case-insensitive behavior and backward compatibility observable through the examples in the issue.