Reverse generation, last_frame, prompt lock, recompute_if(), dangerous(), common prompt start/end, maths on value edit

[rewbs]

• Reverse generation option
• Update prompt frame positions if frame lock is seconds/beats and fps/bpm is updated.
• last_frame context variation
• recompute_if() and dangerous()
• allow maths expressions when editing value cells
• common prompt append/prepend option
• Move options that affect more than just the grid out of the grid section and into their own options section.

[github-actions]

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