Support stereo input in Bias FX2 plugin

[killergege]

One feature I really would like in the Bias FX2 plugin is to be able to feed it with a stereo signal, which I could route to a dual amp patch, one amp for each channel.
Today it seems that you have to have the splitter, and you have to feed both amps with the same signal.
Surprisingly it looks like that the standalone version is able to do that !

This would be really useful as it would reduce the amount of VST instances you need and reduce the amount of screens you need to open when tweaking your sound.