Fix CR Newlines:ExpressionEvaluatingMessageHandler

Lines terminated with CR instead of LF
INT-3126: Document DefaultScriptVariableGenerator

JIRA: https://jira.springsource.org/browse/INT-3126
Doc Polishing for the AMQP Support

Documentation for configuring an external listener container in
the inbound endpoints.
INT-3164: Fix Scripting Refresh

Previously, there was no logic to check, if a JSR223 script
was modified should be refreshed from the external resource.

* Fix `RefreshableResourceScriptSource` to take care of refreshing
on call `isModified()`
* Add `scriptSource.isModified()` before getting script text
* Introduce `ScriptSourceFactoryBean` to avoid I/O operations, when
there is need to refresh script resource - `refreshDelay < 0`

JIRA: https://jira.springsource.org/browse/INT-3164

INT-3164: change the refresh mutation logic

Remove factory bean - no longer needed.
INT-3162 Fix AbstractScriptExecutor Thread-Safety

JIRA: https://jira.springsource.org/browse/INT-3162
INT-3091 Fix Concurrent (S)FTP Transfers

byte[] and String payloads were written to a temporary file.

If the same message is transferred to two different destinations
concurrently, one of the adapters could remove the temporary
file while the other was using it.

Don't use a temporary file for these payloads, simply use the
payload byte[] [or a String.getBytes()] as the InputStream
passed to the Session.write() method.

Polishing

Polishing - Add WARN For Missing File

+ Test

JIRA: https://jira.springsource.org/browse/INT-3091