Aux switches: add "release, hold release and double" press types

[MarkFSI]

Hello,
the content of this proposal is well summarized in the title;
to take full advantage of the "switch in" flexiports mode, I think they should be added the following press types:

• release
• hold release
• double press

I give you an example of my experience of use:
I've had the need to add another external switch to my Bridge6 with the purpose of send some messages on "press" and "release" press types.
I had a keyboard footswitch available with TS jack connector (switch pressed = closed circuit, switch released = open circuit) but I couldn't use it as it was, I had to modify it to have a TRS connector and the following way of operation: switch pressed = TS closed circuit, switch released = RS closed circuit.

With the improvement I'm suggesting:

• first the user doesn't have to modify the external footswitch
• furthermore one flexiport can connect not only one, but two of these external footswitches, with the same functionality that I have now