Fix 409 based on melodic branch

[Tuebel]

Based #409 on branch melodic.
Also removed boost::mutex and boost::shared_ptr in favor of the std types.

The constructor of the dynamic_reconfigure::Server requires a boost::recursive_mutex so in this version I use the constructor without the mutex parameter. But as far as I can tell from the code of the server the mutex is only required when calling dynamic_reconfigure::Server::updateConfig(const ConfigType &config) which we don't.

[knorth55]

I'm not familiar with image_transport, but does this PR work when there is no camera_info topic?
It seems image_transport uses message_filter so that this PR change to require both camera_info and image.
Current node can resize with only image topic or camera_info topic.

[Tuebel]

@knorth55 image_transport::CameraSubscriber indeed needs both topics synchronized and you do have a good point. We should not brake compatibility, so I will try to implement the best of both by using image_transport::Subscriber for images and a ros::Subscriber for the CameraInfo.

[JWhitleyWork]

@Tuebel - Since this is a back-port, can you also create a PR to apply any changes you make here to melodic?

[knorth55]

@Tuebel
Thank you for checking it.
Many people use resize nodelet to resize image only, so it is good to support previous behavior.

@JWhitleyAStuff
This PR is a back-port, but current PR changes previous behavior (message synchronizing part).
I think it is better to wait @Tuebel update and merge after it.

[Tuebel]

@knorth55 I pushed an implementation, which allows to resize the image and the camera_info independently. The images are published and subscribed using the image_transport classes so we still get the functionality of the plugins. I also kept an eye on making only the necessary changes compared to the old resize.cpp.

@JWhitleyAStuff I'm sorry but I don't understand what kind of different PR should I create?

[JWhitleyWork]

@Tuebel - Nevermind. I was confused. There are many tickets in-flight right now and I got them mixed up.