Fixed implementation of REPLACE() to properly handle captured values.
Fixed bug in BNODE(str) generation that wasn't respecting the current solution mapping identity.
Added support for evaluating unary minus expressions.
Removed debugging output.
Fixed bug in GTWTree nonAggregatedVariables method that was returning non-variables.
Fixed bug in SPARQL parser handling ordering of BGP, Filter, Extend, Left join, and Minus.
Added support for evaluating != expressions and xsd:integer and xsd:double cast functions.
Fixed bug that was failing to rewrite alias variables for aggregates in nested expressions.
Fixed ordering of FILTERs that appear inside GRAPH blocks (now pushed above the graph algebra).