Make default path to coefficient files relative to path to library
Currently the EveryBeam installation is not relocatable. The CMAKE_INSTALL_PREFIX variable is written into a #define in a config.h file The coefficient files for a number of ElementModels are found using these defines. When after installation the prefix is renamed/moved/mounted under a different name, the coefficient files can no longer be found.
Making the path to the coefficient files relative to the path to the EveryBeam library makes the installation relocatable.