INT-3288 JMS 'session-transacted' Attribute

JIRA: https://jira.springsource.org/browse/INT-3288

Previously, if you wanted to have a JMS outbound-channel-adapter
participate in an upstream JMS transaction (or use transactions
at all), you had to inject a `JmsTemplate` with `sessionTransacted`
set to `true`.

The `session-transacted` attribute has been added to the adapter,
allowing transactions to be used with the default `JmsTemplate`,
avoiding the need to inject a separate template.

Also, the inbound (polled) channel adapter incorrectly allowed
the `acknowledge` attribute to be set to `transacted` which is invalid and,
again, you had to inject an appropriately configured JmsTemplate
for transactions.

The inbound-channel-adapter now supports `session-transacted` as
well, and `acknowledge` can no longer be set to `transacted`.

There are no changes to the `message-driven-channel-adapter`, you
enable transactions with it by setting `acknowledge="transacted"`
as before.

INT-3288 Doc Polishing; Integration Tests
INT-3305 SFTP Connect Error Polishing

* Add code to test to wait for server to start
* Avoid NPE when trying to close a Sesion that was never open