Update sequencer syntax

[luistoledo]

After using it, I discovered some inconsistency and figured out updates in the sequencer syntax, without breaking the simplicity of the interpreter and the unfold internal sequence (an array of integers).

basics

So a new basic syntax blueprint can be as follow:

1. Basic sequence: 1, 2 ,3
2. Random preset: 1, r, 3
3. Ranges: 1-5 ⇒ [1,2,3,4,5]
4. Repetition: 3x2 ⇒ [3,3]
5. Mutation: 9m
6. Not change: 1, , ,4 ⇒ [1,1,1,4]
7. Skips: 1,2s5,3 the chances to skip the second preset are 5/10

Note on implementation: if the system re-process the sequencer input each replay loop, it will avoid modifying the unfold sequence structure, and will only require a couple of extra global playback counters

looping

New commands for loop control:

1. Ping pong loop: 1,2,p
2. Restart loop (current and default behavior): 1,2,l
3. No loop: 1,2,s
4. Number of repetitions: 1,2,L2 or 1.2,p2 repeats the sequence only twice

Looping behaviors should be set from an external function

groups

Grouping and group functions may be useful for advanced non-linear features:

1. Simple groups: [1,2], [3-1] ⇒ [1,2, 3,2,1]
2. Random from range from a sub-sequence: r[1,2,3] will pick a random preset from the group
3. Repetitions: [1,2]x2, 5 ⇒ [1,2,1,2,5]
4. Group jumps: [1,2]s2, 1 produces a 2/10 chance to skip the whole first group