Better Field Access Support

Added support for retrieval of multiple fields at a time
for a SugarEntry.  When passed a tuple as a key the the return
value is a tuple, with the entries for each key.  This
facilitates reduced HTTP overhead as multiple fields can be
pulled in a single request.
Add Field Support for Queries

When creating Queries you can now provide a list of result
fields that should be retrieved.  These should be set
when query() is called, and are carried through during
filters and excludes.