AMQP filter expressions

I didn’t manage to completely get the homework done on the filter expressions, but I did make a good amount of progress.
It’s too early to upload it as a draft, but here’s a link to the doc that I’m working on: https://1drv.ms/w/s!
AgcBsXoqzTwSrd0pF0LUORZikSgmiA The SQL _expression_ syntax is lifted from the Service Bus product docs and I need to do some trimming.