"Global: Set automation mode override": Add "None" option

[helgoboss]

At the moment, "None" is the 0% value of both "Behavior" options. So it's triggered when releasing the button. Now one could think that one should set Target Min/Max to 0% to also trigger it on button press! But no, this doesn't work if we currently have another global override. Because the current value will be 0% and therefore the mode thinks it doesn't have to do anything.

There are 2 ways to approach this:

1. Add an explicit "None" option.
   • Analogously to transport target (has Stop and Pause also as 100% options) and track automation mode target (has Trim/Read also as 100% option).
2. Make this a trigger target

Should consider both. And maybe make transport and track automation mode target also trigger targets.

[helgoboss]

I actually meant retriggerable instead of trigger. Making a target retriggerable always makes sense (in this context) if the fact that the target reports 0% as the current value just means that it doesn't have the specified value (e.g. automation mode override "Write") but doesn't necessarily mean that it has the 0% fallback value (if there is a 0% fallback value at all). This can happen with all on/off targets that actually can also be expressed as a target with multiple distinct values - like an enum. This includes:

• Global: Set automation mode override (fallback value being "None")
• Track: Set automation mode (fallback value being "Trim/Read")

It's not the case for target "Project: Invoke transport action" because for all variants, reporting 0% really means it has that value. But it's still nice to make it retriggerable for actually being able to retrigger play! So we should do it if action is "Play/stop" or "Play/pause".