collection/bug: if no elems are removed in a put, splice is weird.
model/bug: shadow parent not getting set early enough.

* needs to beat _initialize().
model/bug: don't spuriously serialize empty hashes.
model/experimental: auto-collapse of reference values on get.
model/new: add ModelResolver.
store/bug: complete request state should take result.
util/new: add once() and hasProperties() calls.