Feature request: Compiling JANA as a CMake subproject

[DraTeots]

Currently JANA2 uses CMAKE_XXX where it should use CMAKE_CURRENT_XXX. As CMAKE_XXX is now corresponds to a parent CMake project.

[nathanwbrei]

@DraTeots I gather we have to change all of our references to CMAKE_SOURCE_DIR to CMAKE_CURRENT_SOURCE_DIR. Any other variables that you know need to be changed?

I'm assuming that CMAKE_INSTALL_PREFIX,CMAKE_BUILD_TYPE,CMAKE_CXX_*, etc, should inherit from the parent project.

[DraTeots]

@nathanwbrei if you put a PR with that I can test and we'll figure out if there is something else

[nathanwbrei]

@DraTeots Are you compiling JANA2 as a CMake subproject? If it works I'd like to close the issue.