Major milestone: we can now render multi-stage QL

Two main enhancements here:

First, we can *mostly* do multi-Stage.  It's a bit fragile yet -- I need
to improve the parser -- but you can use the arrow operator with care.
So you can build a proper Pipeline, probably of arbitrary length.

Second, we now have a well-defined concept of embedded QLText.  You can
specify a QLText inside a QL Expression using double-double-quote.  This
recurses nicely into the processor, so it can contain further embedded
QL, allowing you to build complex renderings.
Fixed the whitespace handling in QL