Added some useful features

[holgerl]

Hi Vitling!

I am a huge fan of your work, both in music and in code. I am fascinated by this AutoTracker and have listened to it a great deal. I have for a long time thought about some simple features that would be of great value to me and maybe others, without interfering too much with the original work. In this pull request, I have implemented them, and I really hope that you would be able to consider taking them into your main branch.

I have made separate commits for each thing:

• Add checkbox for disabling automatic regeneration of new patterns, and button that forces a regeneration once
• Make it possible to mute a track by clicking its title
• Ignore exception that happens when AudioParam.setValueAtTime is called during a curve event. It has no effect on the sound, and fills up the console log
• Remove the value for veloctiy in bass2, as it is not used in the sound generation for SquareSynth, but makes the ui display "v1FE"
• Add favicon