Implement partitions over Domains.

[dariavh]

Short description

This PR will provide new features regarding the partition of domains, electron numbers and orbitals over the Domains defined by GQCP.

Related issues Closes #1049.

To do

• [x] (if applicable, when creating new source files): don't forget to update the Doxygen file, the collective gqcp.hpp include header and the CMake files
• [x] Implement SimplePartition as a base class for all partitions.
• [x] Implement DomainPartition as a base class for partitions of domains.
• [x] Implement DiscreteDomainPartition that divides a discrete set of orbitals into domains.
• [x] Generalize functionality overlapWithONV from HubbardDomain to DiscreteDomain.
• [x] Implement ONVPartition to create new ONVs for each (discrete) domain separately.
• [x] Implement ElectronPartition (spin-unresolved and spin-resolved) to specify the electron occupation in each domain.
• [x] Write tests.
• [x] Write Python bindings.

[dariavh]

@xdvriend This PR is quite a bulky one because I introduced a lot of new Partition-related implementations. I have rebased this branch with develop to allow for working Docker containers again, but this rebase added a lot of files that do not need your review again. The files unique to this PR are in the Domain and Partition folder (hpp, cpp, test and bindings). I have also added the calculation of probabilities of finding a given distribution of electrons over a set of domains to LinearExpansion.