function f(n) {
        // Format integers to have at least two digits.
        return n < 10 ? '0' + n : n;
    }
Perform a query
@param  {string} q the user query
@param  {function} searchCallback the result callback called with two arguments:
 success: boolean set to true if the request was successfull
 content: the query answer with an extra 'disjunctiveFacets' attribute
@param {hash} the list of search parameters