- Modify CMakeLists to avoid warnings in VS 2013 64 bit builds (/arch:SSE2 unrecognized). SSE2 is the default for that compiler.
- Fixed caching problem that prevented BUILD_INST_SET changes from taking effect. This required removing the compiler command line variables from the cache; those are no longer changeable from CMake.
Merge pull request #88 from simbody/avoidWarningsInVS12Win64

Modify CMakeLists to avoid warnings in VS 2013 64 bit builds.
Fix doxygen comments for Force::Gravity. Fixes issue #80.
Merge pull request #89 from simbody/fixGravityComments

Fix doxygen comments for Force::Gravity.