Migrate to ROS2-Rolling.

Rolling changes exposed a few old bugs. These fixes could be backported:

• teleop_node depends on cv_bridge
• make build_world.py executable
• use empty.world as a build target, not simple.world (which doesn't exist)

Some build requirements were updated:

• CMake minimum is 3.14 (since Galactic)
• C++ version is C++17 (since Galactic)

Other changes:

• tf2_geometry_msgs/tf2_geometry_msgs.h is deprecated, use tf2_geometry_msgs/tf2_geometry_msgs.hpp
• Dockerfile was re-written to use workspace.repos
• Remove old CLion sections from make files

Resolves #13