Cmake

[loriab]

• [x] looks for external armadillo, libxc, integratorxx rather than hard-coded local paths
• [x] installs headers and dummy config file to the right place
• [x] uses OpenOrbitalOptimizer throughout but doesn't rearrange dir structure for repo
• [x] builds atomtest and runs two samples through ctest (no actual checks though)

sample build line:

rm -rf build/ install1/ && cmake -S. -Bbuild -DCMAKE_INSTALL_PREFIX=/psi/gits/openorbital/install1 -DBUILD_TESTING=ON -DIntegratorXX_DIR=/psi/gits/IntegratorXX/install1/lib64/cmake/IntegratorXX && cmake --build build --target install && ctest --test-dir build/

with libxc, armadillo through conda, and integrator through local install