PaccMann family update

[jannisborn]

All PaccMann based models, e.g. proteomic and omics based generator should be retrained using the pypi-distribution of pytoda. This will enable all paccmann-related repos in vcs_requirements.txt to be pip installable and could free us almost entirely from the vcs requirements. This will affect inference of PaccMannRLProteinBasedGenerator and PaccMannRLOmicBasedGenerator