Hardware Echo Support

[bazz1tv]

Echo is so close to being fully implemented ;)

Once I impl the Checkbox #50 , it will get added to set or unset echo for any instrument via the instrument editor window.

I've already impl'd most else to get it working, currently greyed out in Song Settings. I'd like to make those feel more intuitive as well.

My 'extra credit' is to add a dropdown of known preselects for the FIR filter coefficients, with ability to manually override, and uses a system default of 7f 0 0 0 0 0 0 0