Numeric request parameters serialized to JSON as strings

[killvetrov]

When using Request.setContentType(NConst.MIME_TYPE_JSON) all parameters added via addParam are serialized as strings:

{"projectId":"471","text":"","status":"pending approval","fileId":"7230"}

In some cases there is a requirement for numeric type in JSON (fileId in this example):

{"projectId":"471","text":"","status":"pending approval","fileId":7230}

In current version 1.4.2 there is no way to serialize parameter as a number.