Small callcount reductions and refinement for cached queries

Small callcount reductions and refinement for cached queries

baked wasn't using the new one()/first()/one_or_none() methods,
fixed that.

loading._instance_processor() can skip setting up the
quick populators every time because it can cache the getters.

Callcounts have gone below what 1.3 does for the
test_baked_query performance suite, however runtime for
continued inexplicable reasons has not :(.   still suspecting
the result tuples but this seems so hard to believe.

Change-Id: Ifbca04834d27350e0fa82cb8512e66112abc8729