frame picking

[wwerkk]

could do with a few modes which would change behaviour of picking the frame of a given class from the dictionary when a grain is being triggered:

• locked n-th frame only
• random (as it is now)
• sequential (from first to last frame of given class, could us a table object to save state per-token)
• sequential (from last to first)
• mixture between the above, ie. using a markov chain or other means of controlled randomization

[wwerkk]

choices of locked, sequential and random added with https://github.com/wwerkk/MC-FP/commit/24c75dc4c2bf19f0a39acf8aee55dfec3beee1c8 drift mode with parametrised chance added with https://github.com/wwerkk/MC-FP/commit/4273a15c1b8d6e337e236d3840665cee310a915d