Fixed a broken return.

without the create flag. This was reported by intrepid win32
Zopistas.  Why did it work on Unix?

Changed to use has_key rather than get to work with older mapping objects.

Added important note in constructor.

Changed to use keys() rather than items to iterate over
the index.

  - Provides a relatively simple example for building full storages,

  - Is useful for giving demos because it is non-persistent.

Took out incomplete code for allowing a base base storage.  Base storages
are trickier than they first seem.

in transaction writing *just* in case a system crashes during the last
step of commiting a transaction.

all transaction aware storage managers recognize subtransactions.

(in another connection).

pool to go south when there were more app threads than connections.

during an active transaction.