Minor Fixes and Improve Code Coverage

What's Changed

• Add sub-directories for external dependencies of tesseract_collision by @Levi-Armstrong in https://github.com/ros-industrial/tesseract/pull/649
• Remove dynamic_cast in tesseract_compound_collision_algorithm.cpp by @Levi-Armstrong in https://github.com/ros-industrial/tesseract/pull/650
• Fix issues in kinematics plugin factory by @Levi-Armstrong in https://github.com/ros-industrial/tesseract/pull/652
• Add ability to load contact managers as plugins by @Levi-Armstrong in https://github.com/ros-industrial/tesseract/pull/654
• Improve tesseract_environment code coverage by @Levi-Armstrong in https://github.com/ros-industrial/tesseract/pull/655

Full Changelog: ros-industrial/tesseract_repos@0.6.2...0.6.3