Merge branch 'feature/make_operator_shortcuts' into 'develop'

add shortcuts zot(), fot(), and sot() for backward compatibility/similarity with old AMDiS

See merge request !97
Status Job ID Name Coverage
  Test
canceled #8709
debian:10 clang-6-libcpp-17

canceled #8708
debian:10 gcc-8-17

canceled #8710
debian:9 gcc-6-14

canceled #8711
ubuntu:18.04 clang-6-17