Highlights:

BaseStorage.py:

Fix copyTransactionsFrom() when commitVersion(), abortVersion() or
transactionalUndo() is used.

FileStorage.py:

Add restore() method, which can store data records corresponding to
undo or version manipulations; add close() method to FileIterator
class; raise POSKeyError instead of KeyError for bad keys, to ensure
safe formatting of transaction ids (binary strings) in tracebacks.

POSException.py:

Add POSKeyError.

fsdump.py:

Deal with records indicating the undo or abort of a version doing
object creation.

tests/IteratorStorage.py:

New unittests for the iterator() method and interface of the
storage API; new unit tests for extended file iterators; new class,
IteratorDeepCompare; test of the iterator .close() method.

tests/testFileStorage.py:

Add class FileStorageRecoveryTest, which adds two simple tests for
copyTransactionsFrom().  This indirectly tests the new restore()
method.