First step in ND vectorized systems
Before proceeding with the ND systems and a new format (#316) we should make an intermediate step, which would not break the consumers, but enable further improvements.
This would contain the following changes:
- Move symmetry to system
- Annotate all Hamiltonian terms with a symmetry group element
- Stop storing sites in the neighboring unit cell within the infinite system
- Mimic the old interface (sites, hamiltonian, inter-cell hopping)