Add class member method callback support for Service Server.

[romainreignier]

Based on the work done for the Subscriber (#241).

I did not manage to add test because there are conflicts with the full Ros version.

Here is a simple test for Arduino:

#include <ros.h>
#include <std_srvs/SetBool.h>

ros::NodeHandle  nh;
using std_srvs::SetBool;

class MyClass
{
  public:
    static void callback_class_static(const SetBool::Request& req, SetBool::Response& res)
    {
      res.success = true;
      if (req.data == true)
        res.message = "Class static method: true";
      else
        res.message = "Class static method: false";
    }

    void callback_class(const SetBool::Request& req, SetBool::Response& res)
    {
      res.success = true;
      if (req.data == true)
        res.message = "Class method: true";
      else
        res.message = "Class method: false";
    }
};

MyClass mc;

void callback_non_class(const SetBool::Request& req, SetBool::Response& res)
{
  res.success = true;
  if (req.data == true)
    res.message = "Non-class: true";
  else
    res.message = "Non-class: false";
}

ros::ServiceServer<SetBool::Request, SetBool::Response> server_non_class("non_class_srv", &callback_non_class);
ros::ServiceServer<SetBool::Request, SetBool::Response> server_class_static("class_static_srv", &MyClass::callback_class_static);
ros::ServiceServer<SetBool::Request, SetBool::Response, MyClass> server_class("class_srv", &MyClass::callback_class, &mc);

void setup()
{
  nh.initNode();
  nh.advertiseService(server_non_class);
  nh.advertiseService(server_class_static);
  nh.advertiseService(server_class);
}

void loop()
{
  nh.spinOnce();
  delay(10);
}

[mikepurvis]

I dig it. Thanks for contributing this!