CMake for building API examples is unclear

[chrisdembia]

In preparation for making the opensim installation more unix-friendly, I am cleaning up the cmake files for examples. I have some questions.

1. SymbolicExpressionReporter does not get installed (https://github.com/opensim-org/opensim-core/blob/master/OpenSim/Examples/CMakeLists.txt#L16).
2. The block of code starting at this line never gets executed.
3. What should be the behavior of the cmake variable BUILD_API_EXAMPLES? Right now, what it seems to do is prevent the installation of files; it does not affect building. Is this correct?

[sherm1]

Related to issue #195, I think.

[chrisdembia]

Related to issue #195, I think.

yep

[jenhicks]

@aymanhab related to #195 ... thoughts on the status of thsi one?