G4 generate patterns for an experiment

[floesche]

• Generating pattern one (relates to above comment also). When explaining about changing the contrast, there is no explanation for what contrast levels are (gs level of 4bits).
  basically, add also what are the acceptable values not just what you use in the example.
• Do you have an option in the GUI to add an empty frame to a pattern? Newcomers should read about this option somewhere in the documentation since it is important when running experiments.
• Next steps - since it wasn’t explained what patterns are it is also not clear what position functions are. If you say that patterns are 4D matrices with the 3rd and 4th dimension controlling how the pattern changes (with the grating example it would be just 3rd dimension creating the movement) then you can state the position function tell the controller which frames in the 3rd dimension to present and when. (something like what is in the overview for the G4_function_generator)

This issue is part of the second feedback round, received 2020-10-26.