Add diff-based incremental code editing

[dipamsen]

(Don't merge this because this probably introduces a lot of bugs in the streaming code, and also switches to non-stream instead of streaming)

The latency can be improved by going back to streaming, and collecting all code chunks, and performing the diff.

Another parameter to be fiddle with could be the delay timings between the various events (code typing, deletion, selection, etc.)

[dipamsen]

now obsolete by #62 !