Various performance updates (as a result of brute force profiling), major restructure:
Various performance updates (as a result of brute force profiling), major restructure:

- additional partition for literals.  Triples are put here *only* if the object is a Literal
- configurable term typing control.  This controls how the literal partition is searched and
  could have some huge performance gains for *very* large graphs that are searched with REGEX expressions

- term caching

- other refactoring 



git-svn-id: 60eb48102d1ca0c284ab3654bef916b01e1b221b@482 4f84a9ca-5c3e-0410-8a68-0bdf370325d5

nwebs/rdflib