Make rct_image_tools a pure CMake package

[schornakj]

This depends on #42 and continues to address #35.

• Modify rct_image_tools to be a pure CMake package, instead of a Catkin package.
• Provide rct_image_tools libraries through the rct::rct_image_tools target.
• Modify packages that use rct_image_tools so that they treat it as a CMake package instead of a Catkin package.
• Link against Eigen using the Eigen3::Eigen target.
• Use the macros in rct_common for package setup.

[marip8]

@schornakj do you know why CI hasn't run for this PR? It looks like your branch has the CI config files. Maybe it needs a rebase or we need to close and reopen this PR?

[schornakj]

@marip8 I've read that Github Actions have some poorly-documented limitations that sometimes prevent jobs from running. I need to push up a new commit to trigger the pipeline again.

[Levi-Armstrong]

B

[schornakj]

@Levi-Armstrong @marip8 The current problem is that the Eigen3::Eigen target isn't provided by default on Xenial. I have a section in rct_image_tools/CMakeLists.txt that creates this target from the Eigen3 definitions and include directories if it isn't found. However, it looks like packages that link against rct_image_tools aren't able to find my Eigen3::Eigen target.

What's the right way to solve this, other than duplicating the creation of my Eigen3::Eigen target in each package that links against rct_image_tools?

[schornakj]

@marip8 Added a workaround for the Eigen issues I'd been having in the name of getting some of the outstanding PRs resolved. Should be ready to go.