Designing a LimbBase class

[jdcaporale]

Expanding on PR #67 based on Issue #48 ,

From there,

Created a LimbBase class between JointBase and RobotBase

• Fully abstract base class with pure virtual kinematics and helper functions
• Incorporated into RobotBase with AddLimb function
• Simple_Limb example for 1DOF limb with joint at origin and straight end effector
• Testing in robot_example still a work in progress, having trouble compiling

What I added:

• Caching for kinematics and updated kinematic functions / logic.
• Helper functions, e.g. new joint_utils namespace
• a 3DoF example, needs some work and testing

Still working out:

• What type of configuration is needed for limbs
  • Letting the user-made classes handle that might be beneficial
  • Also making a general RRR limb could be useful
• How could we handle multiple output options?
  • e.g. We often like having legs in polar and in cartesian, should the user make separate limbs with converting member/free functions or have a std::pair output or they add their own FKPolar function?