Matt ayman frames

Redo of the merge of Frame, RigidFrame, FixedFrame, Station and Marker ModelComponents along with code to convert Marker to new format for serialization/deserialization and inclusion of FrameSet in model.
@sherm1 @msdemers @aseth1 or @chrisdembia Please review and let us know your feedback.
@chrisdembia good question.  Per Ajay's request, RigidFrames can be fixed to MobilizedBodies even if they are not fixed to OpenSim::Bodies.  Thus this method is needed to check if this FixedFrame attaches to a Body at all, not just if it's anchor body is currently set.