Writing out variables to config.h from the main CMakeLists.txt does not work as well as writing it out from AMD/CMakeLists.txt. Also, removing AMD_HAVE_BOOST as this is a pointless macro to have. Boost is required, so when AMD_HAVE_BOOST is 0, we don't even bother compiling
Fixing the position of add_subdirectory(AMD) to be after Elemental checks but before tests subdirectory. Also, fixing a bug with the Python option