[WIP] Create DiscreteHilbert (AbstractHilbert<:DiscreteHilbert<:...)
Created by: PhilipVinc
Renames AbstractHilbert
to LatticeHilbert
.
AbstractHiblert
becomes more fundamental, and does not assume a lattice/discrete space anymore so that it can be derived from for continuous spaces without doing odd things.
The name LatticeHilbert
should be thought a bit more about.
Also some functions like size_at_index
should be thought about.