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.
No, a general Frame is not a rigid massless Body. Since Frame includes floating Frames, you can only apply forces and connect joints to a RigidFrame since only a RigidFrame has the requirement of be backed by a MobilizedBody.   I understand that it is difficult to explain what abstraction a RigidFrame, but that doesn't mean its not a useful one.