Audio Visualiser/Shadertoy Music Player

Initial package/demo of a shadertoy-based music visualiser

Changes
* Shaders no longer auto-rotate - Select on in the toolbar, or press x to cycle
* Press F11 to go fullscreen
* Basic UI added, Press F12 to hide (Small performance gain with UI disabled)
* Lots of rework, internal changes/build infrastructure to make my life easier
* Permissions fixed on opengl-visualiser.sh in Linux package
* Visual Studio runtime now included in Windows package (Should run out of the box)

To run
* Download package
* Double click on bin/opengl-visualiser.exe or opengl-visualiser.sh
* Visualiser will loop through music set automatically

Keybindings - Displayed in bottom status bar, few new ones in this release

Music will be loaded from the music folder in the release. mp3 and wav formats are supported so far.

Shaders will be loaded from the shaders folder in the release. See readme in shaders directory for info on shader format (It's shadertoy, with iChannel0 bound to the music data).

Licences
* Executable and repo covered by BSD licence
* Code deps various, see main Readme.md/contents of extern folder
* Music licence listed in music directory. Example music from https://www.bensound.com/royalty-free-music
* Some shaders obtained from shadertoy.com. Licences included in shader wherever available.