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.
I am for having a consistent definition for Station in OpenSim and Simbody. I haven't seen or heard about the solution to the problem I posed about representing, for example, the CoP. 
@sherm1 would you derive Station from a general Point or PointOfInterest? I worry about retrofitting a new base class. If we want the base to at least provide the ability to draw itself it should provide its location in ground. Point then would be analogous to Frame.

@aymanhab  @msdemers then change the use of "reference frame" to "rigid frame"?