Implemented install directory structure discussed in #3
mod files are now installed along library archives/objects,
under `<prefix>/lib/<project>-<version>/<compilerID>/`
Some variables were refactored to, to try to simplify
the CMakeLists.txt file.
Improved readability in top level CMakeLists.txt
Pushed some CMake ugliness to included files
install location: <prefix>/jsonfortran-<conpilerID>-<version>
e.g. /usr/local/jsonfortran-intel-1.0.0