Add "Sort by Channel" to mixer view

[pljones]

What is the current behaviour and why should it be changed?

Currently, when "No user sort" is specified, "faders are sorted in the order they appeared" -- and sometimes (quite rarely) this isn't the same as the channel number:

Because --ctrlmidich uses the channel numbers to assign Jamulus channels to MIDI controllers, it improves user experience to be able to sort the faders to match and this is not currently possible.

Describe possible approaches

The existing "No user sort" could be replaced with or have its meaning changed to "Sort by channel".

However, this might not be what all users want and invalidates the current definition, so I'm proposing that "Sort by channel" is a new option.

I'm also proposing to extend the "and then by name" to the other non-unique sorts: City and Group and ensure Group sorts properly numerically.

Plus refactoring what's clearly a switch from a bunch of if .. else if .. statements into a proper switch.

Has this feature been discussed and generally agreed?

This arises from the changes recently to --ctrlmidich - just something I thought of.

[pljones]

jamulussoftware/jamuluswebsite#1059 raised to get the documentation change done.