Bank upgrade

[gitpeterwind]

Refactoring of Bank. Main changes:

• Moved all Bank related to own files utils/Bank.cpp
• The usage of the Bank is now through the BankAccount class. Once a type BankAccount is defined, it can be used similarly to an array (or rather a std::map) to put and get orbitals or data.
• The BankAccount are private, so no interference between different parts of the code.
• One can open several BankAccounts (for Bra and Ket orbitals for example).
• They are cleaned up automatically (destructor) when getting out of scope.
• Note that BankAccount class declaration (creator) is collective, i.e. it must be declared by all MPI at once.
• Slightly faster

[codecov[bot]]

Codecov Report

Merging #362 (83500d5) into master (f51902e) will increase coverage by 0.07%. The diff coverage is 29.29%.

@@            Coverage Diff             @@
##           master     #362      +/-   ##
==========================================
+ Coverage   69.08%   69.16%   +0.07%     
==========================================
  Files         171      171              
  Lines       13290    13298       +8     
==========================================
+ Hits         9181     9197      +16     
+ Misses       4109     4101       -8     

Impacted Files	Coverage Δ
src/driver.cpp	70.31% <ø> (-0.05%)	:arrow_down:
src/parallel.cpp	82.60% <ø> (+33.79%)	:arrow_up:
src/qmfunctions/OrbitalIterator.cpp	43.08% <0.00%> (ø)
src/qmfunctions/OrbitalIterator.h	100.00% <ø> (ø)
src/qmoperators/two_electron/ExchangePotential.h	40.00% <0.00%> (-10.00%)	:arrow_down:
src/qmoperators/two_electron/ExchangePotentialD1.h	100.00% <ø> (ø)
src/qmoperators/two_electron/ExchangePotentialD2.h	100.00% <ø> (ø)
src/scf_solver/GroundStateSolver.cpp	89.68% <ø> (-0.05%)	:arrow_down:
src/scf_solver/SCFSolver.cpp	95.83% <0.00%> (ø)
src/qmfunctions/orbital_utils.cpp	67.64% <20.83%> (+0.26%)	:arrow_up:
... and 5 more

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[stigrj]

This looks like a good step in the right direction. One general problem we have is that the MPI parts are not very well tested, so we should get a few unit tests up and running here. I also had to disable MPI for the integration tests some time ago since they refused to launch correctly after runtest was removed. I will try to set up a testing framework for the banking, then I might come back to @gitpeterwind for help with making actual tests.

[gitpeterwind]

Yes, a lot of tests including MPI would be useful. It would however not be a big disadvantage to run those outside github.

[gitpeterwind]

I plan also to make new PR relatively soon, which also include some changes on the Bank (I also put the "enum" requested by @robertodr ). So if there are changes to be made in this PR, it would be better to take it into the new directly.