- refactor query._get() into two methods - a static one that does

- refactor query._get() into two methods - a static one that does
just the identity map lookup + expired check, the other
which does the load unconditionally.  All the refresh/deferred load
calls use the unconditional load method, query.get() and
LoadLazyAttribute call the identity check by itself first.   m2o
lazyloads for object already in the identity map callcounts are
now cut in half, since no Query object is created.