Support for improved virtual orbitals in EXX and RSF
The is the third of a series of four merge requests. It includes the possibility to apply a modified Fock operator to the unoccupied states, such that these states approximate excitations and not affinities. It does not rely on MR !382 (merged) or MR !389 (closed), however: as these states are very usefull for RSF and the calculations of CTEs by GS calcs,see doi:10.1021/acs.jctc.8b00238 for more