[LAD] New version of JackMix

I was attracted by the small (memory and screen) footprint of JackMix, the Qt Matrix Mixer for Jack, which makes it very useful on laptops, but needed to be able to control it via MIDI. This lets us give performances at conferences when we can't afford to talk the whole ensemble. We play a video along with the live musicians feeding separate mixes to each performer and to master speakers from multi-track video being played by the VLC Jack plugin. Consequently, I've updated it to make the mixing elements respond to MIDI control commands. My updated version is here: https://github.com/nickbailey/jackmix If the original author, Arnold Krille, is reading this, I'd really like to email you, Arnold. There are one or two things I'd like to change but don't yet understand the best way to do it! Here is the NEWS file: VERSION 0.5.0 ------------- New features this version (added by Nick): The right-click on the matrix can be a bit fiddly to pop up the context menu instead of the knob setting spinbox, so the following shortcuts are now available: * Toggle element selection with Shift-Mouse1 * Replace selected elements with Ctrl-Shift-Mouse1 in the upper- left-most selected element MIDI control of the mixer is now available. You can route signals from a MIDI control surface to JackMix: it appears as "JackMix" in the ALSA MIDI tab of QJackControl, for example. Each element now has an extra context menu entry: "Assign MIDI Parameter". Use should be self-evident. Points to note: * You can't unassign a midi parameter -- it can be set to 0 though (my control surface doesn't have controller 0; some may I suppose). * MIDI control parameter numbers are saved in the xml file generated by File->Save File... menu action, but this means there are extra XML attributes which might upset older versions of JackMix. I've not tested this, but it might cause problems if you aren't aware of the extra functionality.