Merge branch '54-split-currents-cc-into-two-files' into 'master'

Resolve "Split currents.cc into multiple files"

Closes #54

With this merge request we have changed the structure of the code from:

mermaid 
graph TD; currents.hh-->currents.cc;

To the following:

mermaid 
graph TD; Wjets.hh-->Wjets.cc; Hjets.hh-->Hjets.cc; jets.hh-->jets.cc; jets.hh-->Hjets.cc;jets.hh-->Wjets.cc;

See merge request hej/HEJ!64