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 Also, handles to the mobilizedBody and the fixed transform on the mobilizedBody fit the concept of what a RigidFrame is.  A RigidFrame is not the OpenSim representation of a MobilizedBody.  A RigidFrame is more general than that.  It IS any Frame that has a constant transform IN a mobilized body.  One subtype of that is a Body.  Another subtype is a FixedFrame.  A RigidFrame that IS a MobilizedBody could be a different subtype, if you want such a thing.  

This convention and class hierarchy do what both you and I want RigidFrames to do.  I want a user or high level API customer of RigidFrames to not even need knowledge that Simbody or MobilizedBody exist at all.  They just live in OpenSim land.  You want a small population (pretty much just you right now) to tinker with low level mobilized bodies, and therefor have "Advanced Access" to the mobilizedBody.  

From what I've seen this makes both tasks very easy.