INT-3384: Rework JMS/XML Module XSD Enumerations

JIRA: https://jira.spring.io/browse/INT-3384

Polishing
Fix Timing in GemFire Delayer Reschedule Test

https://build.spring.io/browse/INT-MEIGHT-JOB1-166
INT-3412 (S)FTP Append, rmdir, Client Access

JIRA: https://jira.spring.io/browse/INT-3412

Initial commit - review only.

TODO:
- SFTP Tests
- Namespace/Adapter support for file append
- Docs

INT-3412 Polishing

- Addressed PR comments
- Completed SFTP implementation
- Added namespace/parser support for `FileExistsMode` (append, etc)
- Added SFTP Tests
- Created Embedded SFTP server for tests (similar to FTP)
- Converted tests that needed a real server to use the embedded server

INT-3412 Docs and Polish (PR Comments)
INT-3422: Add `ChannelInterceptorAware.remove()`

JIRA: https://jira.spring.io/browse/INT-3422

* Add two methods:
```
boolean removeInterceptor(ChannelInterceptor interceptor);
boolean removeInterceptor(int index);
```

The method `removeInterceptorsOfType(Class<?> clazz)` isn't good, because we lead undesired behavior, when several provided interceptors might be of the same type (e.g. by superclass)
INT-3422: PR comments