- Improve speed,
  - Reduce stuttering,
  - Add request meta-data to transactions.

indexing documents with few than two keywords fails silently rather
than raising an exception.

to make authentication slightly less annoying.

acquisition.

Rearranged init to handle errors better.

overridable method.  This is needed to implement a clear method
in a subclass that allows an inverted index to be "cleared" without
actually updating data records.

Made some slight optimizations.

Got rid of get/setstate.
Made result-list-specific methods use mapping prootcol to make it
easier to mix with other mapping types.

try to avoid one-element tries by storing partial-key/value tuples
instead of sub-tries.

Fixed dealloc bug.

better error handling.

products if DateTime subclasses are mixed with ExtensionClasses.

numbers more easily.

use put2() in save_reduce() and save_inst() only if state is not a dictionary
removed put2() from save_tuple()