* Port depth_image_proc on ROS2

* Port depth_image_proc of image_pipeline on ROS2

* rename Nodelets as Node

* add launch examples, such as "ros2 launch depth_image_proc point_cloud_xyzi.launch.py"

* verified point_cloud_xyzrgb, point_cloud_xyz, convert_metric based on Realsense camera(https://github.com/intel/ros2_intel_realsense).

Signed-off-by: Chris Ye <chris.ye@intel.com>

* add ament_lint_auto test and adjust code style

Signed-off-by: Chris Ye <chris.ye@intel.com>

* update test example for depth_image_proc

- rename raw topic as image_transport fixed the issue (ros-perception/image_common#96)
- update test example of point_cloud_xyzrgb.launch

Signed-off-by: Chris Ye <chris.ye@intel.com>

* remove unused dependence in cmakelist

* remove boost which is unused on ROS2

* remove cv_bridge version check logic as setted in find_package

* update maintainer in package.xml

Signed-off-by: Chris Ye <chris.ye@intel.com>

* added all example launchers for demo test

pass test:
 ros2 launch depth_image_proc point_cloud_xyzrgb.launch.py
 ros2 launch depth_image_proc point_cloud_xyz.launch.py
 ros2 launch depth_image_proc convert_metric.launch.py
 ros2 launch depth_image_proc crop_foremost.launch.py
 ros2 launch depth_image_proc point_cloud_xyz_radial.launch.py
 ros2 launch depth_image_proc disparity.launch.py
 ros2 launch depth_image_proc register.launch.py
 ros2 launch depth_image_proc point_cloud_xyzi.launch.py
 ros2 launch depth_image_proc point_cloud_xyzi_radial.launch.py

Signed-off-by: Chris Ye <chris.ye@intel.com>

* @wip update to use raw pointers.

* continue to update to use raw pointer

Signed-off-by: Chris Ye <chris.ye@intel.com>

this may be remarked while code debugging, should be enabled to build node plugin file
and added points remap in point_cloud_xyzrgb.launch.py

* port image_publisher on ROS2
* switch to use cmake 3.5
* change nodelet to classloader
* change ros::param to ros2 parameter APIs
* use ros2 code style
* enable ros2 camera_info_manager

… services