Convert to sound

[gb0808]

This is the convert-to-clip block we talked about in today's meeting.

[dragazo]

I think this block is not thread safe because lastConvertBlockClip is a global variable rather than a process-owned variable (so concurrent executions of this block by multiple scripts will mess each other up). Also, is this.recordFlag reset elsewhere? Otherwise multiple of these blocks in the same script will not work.