flat automations by default when created by dragging

[bltzr]

opinions might differ (@thibaudk what do you think, for instance ?), but I think it would be much better that automations be created flat when creating by dragging a cable or an address to an interval.

• What it does now: create a ramp from min to max
• What it should do IMHO: create a flat line with the current value, with the param’s min and max for the automation’s range

[thibaudk]

sure, I agree.