[Midi Backend] Implement hotswap support

[d5tn]

First of all I love to use midimonster in combination with MA2. I've run mulitple shows and even whole festival stages with it and rarely have issues.
But there is one thing that bothers me.

When a midi device configured the the config file is not found or unrespinsive midimonster just throws an error or completely shuts down. I have a midi controller that needs a restart once in a while. This instantly crashes or shutdowns midimonster and I have to manually restart it.

I am also running a bunch of different midi devices and always have to change the config files to the specific current setup. This is why I have a lot different conifg files for different setups which quickly gets messy and complicated.

Is there a way to just create a single config file with all my devices configured and let midimonster constantly scan for those devices and use them if they are available without shutting everything down when one device is missing or lost its connection?

This would make my midimonster experience a whole lot better. It would also enable me to use a headless raspberry to run midimonster.

Cheers

[Spacelord09]

Currently the midimonster doesnt allow hotswap for such devices.

@cbdevnet