* context.h - Changed cdlist::push_back to use a new copy constructor instead of...

* context.h - Changed cdlist::push_back to use a new copy constructor instead of the assignment operator. This is important as Nodes, for example, check that d_nv != NULL in the assignemnt operator.
* node.h - Simplified the constructors, apparently it's ok to write ~ref_count in the template declaration. All the constructed nodes are now the ref-counted ones, i.e. eqNode() will return a ref-counted node.