LFO implementation like in Barcodes

[schollz]

• see https://github.com/justmat/mangl/blob/master/mangl.lua#L435-L479 for how to do params
• all actions should be to update params for loop X
• in update_timer script, check if update_param = X and then update loop X paramers, or if LFO is active in which case it must be updated
• add LFO amp and LFO freq to each loop
• update_timer updates parameters by calculating LFO and adding that to set value and then clamping it