Port ign image to ros2

[JShep1]

No description provided.

[chapulina]

Thanks, @JShep1 , works great! I just had to add ament_export_include_directories(include) for it to compile on my workspace.

I also pushed a few smaller changes on 56a2ac9:

• Added AMENT_IGNORE to the test directory so the linters don't look at it just yet
• Fixed all linter issues. Those can be checked running colcon test --packages-select-regex ros_ign_image and then looking at log/latest_test/ros_ign_image/streams.log, for example.
• Kept the test cmake code commented out so we don't lose track of it.

I'll merge this into #58 and then we can get it all into dashing at once 😄