Make Marker into ModelComponent that derives from Station and modify tools accordingly.
Main changes in Marker:
1. Marker implementing ModelComponent interface.
2. bodyName property changed into Connector to a RigidFrame (in OpenSim::Station)
3. fixed flag has been removed (assumed false, tools now work but will be updated accordingly)

To support Marker functionality, RigidFrame has been amended with method getBody() to return ref. to the Body that the RigidFrame is attached to.
Replace unnecessary const_cast with dynamic_cast (since SafeDowncast doesn't handle const pointers)
Couple more comments.
Merge branch 'matt_ayman_frames' of https://github.com/opensim-org/opensim-core into matt_ayman_frames
Merge .travis.yml from master so that wrapping is not built on gcc.
Up XMLDocument::LatestVersion to account for change in deserializationof Marker, also remove unused method from Marker.
Expose Station to SWIG wrapping so that subclass Marker behaves properly.
Expose Station class in SWIG to fix python test cases
Remove debugging lines and fix authorship in cpp files
Merge branch 'matt_ayman_frames' of https://github.com/opensim-org/opensim-core into matt_ayman_frames

Conflicts:
	OpenSim/Wrapping/Java/swig/javaWrapOpenSim.i
Merge pull request #183 from opensim-org/jimmydDoxygenExperiment

Doxygen layout and format changes. Moved doxygen related files to opensim/doc
[readme] Update travis build status image.

...to reference master branch instead of latest build.
Formatting, doxygen changes, and one code typo.
Add virtual destructors to Frame. FixedFrame, RigidFrame. Remaining new components already have virtual destructors.
Removed Marker::getOffset(), setOffset() which were initially kept for backward compatibility, also used component's connectToModel method directly instead of the public wrapper connectMarkerToModel, updated tools and tests accordingly.
remover MarkerSet public access now that model has addMarker
Update to the RigidFrame interface.  Each RigidFrame now has a getMobilizedBodyIndex(), isAnchoredToBody(), and getAnchorBody() methods to find the base segment to which each RigidFrame is affixed.  Also added logic to Body and FixedFrame for identifying and setting the base segment. testFrame is updated to test this connectivity, including recursively through multiple levels of FixedFrame connections.
Merge branch 'master' into matt_ayman_frames

Conflicts:
	OpenSim/Simulation/Model/PointToPointSpring.cpp
	OpenSim/Tests/Components/testComponents.cpp
Merged and fixed conflicts with latest master.
Fixes to RigidFrame, Body, and FixedFrame that remove bugs for instantiating from xml.