Feature request: Add a "mix all" button

[cryptoarashi]

I'm using whirlpool gui with a remote client and every now and then it just stops mixing and the mix queue is all gone. After I click start none of the outputs is queued anymore, ie. they all somehow get dequeued by themselves. I have to click every output separately to enqueue it, which is a bit annoying when you have like 100 outputs, especially with the laggy UI. Would be great to have an easy way to just queue all post-mix outputs for remixing.