added move constructor/assignment, swap(), remove copy assignment.
added move constructor/assignment, swap(), remove copy assignment.

the idea behind was/is, to eliminate copy constructor/assignment et al,
but i didn't manage to yet as there're some places relying on copy
constructions which weren't easily to rewrite with performance in mind (yet).

christianparpart/x0,christianparpart/x0,xzero/x0,xzero/x0,xzero/x0,christianparpart/x0,xzero/x0,xzero/x0,christianparpart/x0,xzero/x0,christianparpart/x0,christianparpart/x0,christianparpart/x0