Improved qq.obj2FormData method.

* Added support for Array
* Boolean values ​​are replaced by 1 or 0
* NULL values ​​are replaced with an empty string
* undefined values are ignored
* Consider the case when the parameter is a function and returns an Object or Array
* Added helper method qq.isArray
* Simplify obj2url method. Now use obj2FormData to build the query from params