[transaction] Extended TransactionalResource interface

[Stefan Lützkendorf <lu...@apache.org>]

Hello Oliver,
while using MapXAResource and the TransactionalMapWrapper's for implementing
the transient stores for slide I found that the interface TransactionalMapWrapper
has no methods for starting, suspending and resuming a transaction.

So my first draft of AbstractTransientStore has to deal with the transactional
map directly and has to add some extra logic for starting, suspending and
resuming a transaction.

Just for a trail I have extended the interface, added the corresponding calls
to AbstractXAResource and modified MapTransactionalResource.
With these changes the impelementation of slides AbstractTransientStore would
be relly lean and nice.

I attach the corresponding patch at this mail.

This change would require that we adapt slides
  AbstractRDBMSStore.TransactionId
  XAServiceBase.DummyTxResource
too, but I think thats no problem.

What do you think?

Regards, Stefan