G4 tutorial create one condition

[floesche]

• Requirements – link to function generator not working
• Add a position function 9last paragraph) – should read “there are cells”
  Also they do not work exactly like position functions (frame rate is set and they are simply played at an analog output channel not affecting the display)
  Also, instead of useful for certain modes, simply state that can be useful for stripe fixation, so the stripe doesn’t start in the same position always (or a fixed index can make sure the stripe starts in the front or in the back)

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