Add basic_cartesian_example from tesseract_planning

[dave992]

As an addition to #51 I started with the basic_cartesian_example.cpp from tesseract_planning

I currently run into an error with the SimplePlanner which causes the rest of the script to fail as well:

Error:   SimplePlanner failed to generate problem: _Map_base::at.
         at line 93 in /__w/tesseract_python/tesseract_python/ws/src/tesseract_planning/tesseract_motion_planners/core/src/simple/simple_motion_planner.cpp
Error:   MinLengthTask, failed to subdivid!
         at line 137 in /__w/tesseract_python/tesseract_python/ws/src/tesseract_planning/tesseract_task_composer/planning/src/nodes/min_length_task.cpp
Debug:   Error
Debug:   Aborted

I am not sure if it is related, but I also get the following warning about a missing profile:

Debug:   Profile 'cartesian_program' was not found in namespace 'MinLengthTask' for type 'N18tesseract_planning16MinLengthProfileE'. Using default if available. Available profiles:
Debug:   Environment, getJointGroup(manipulator) cache miss!
Debug:   Environment, getGroupJointNames(manipulator) cache miss!
Debug:   Environment, getJointGroup(manipulator) cache hit!
Debug:   Environment, getKinematicGroup(manipulator, ) cache miss!
Debug:   Environment, getGroupJointNames(manipulator) cache hit!
Debug:   Environment, getKinematicGroup(manipulator, ) cache hit!
Error:   SimplePlanner failed to generate problem: _Map_base::at.

Changes I still need to do:

• [ ] Create a viewer instance and visualize the results
• [ ] Fix failing problem generation for SimplePlanner
• [ ] Update readme to include instructions for setting the environment variables before running the example or pass them in via the command line.