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.
@aseth1 Hmm.  I think we mean that a Frame is a rigid, massless Body.  A RigidFrame is a Frame that is ultimately connected to a rigid, articulating segment of the model.  This is similar to one of your higher comments as well.   Maybe "fixed to a Body" isn't appropriate, but what is?  "Articulating Segment", "Segment", "Root Segment", "Anchor Segment"?  It's important to verbally distinguish this from base class Frame.  

Getting a handle to the "AnchorBody" or "MobilizedBody" is part of RigidFrame's interface.  I think this needs to be acknowledged in it's description.