Shape Expressions to SPARQL compiler

I tooled away on <http://www.w3.org/2013/ShEx/SimpleShExDemo> to
compile validating SPARQL queries. If you 'v'alidate, you'll see a
link for a <SPARQL validating query> which captures very nearly all
of the ShEx functionality. More work to do, but it might be useful
to some of y'all in its current form.

-- 
-ericP