XD-2215: Fixed NPE in ZooKeeperModuleMetadataRepository

Modified ZooKeeperModuleMetadataRepository to eliminate NPE.

Introduced Id class to ModuleMetadata, which is used
to identify instances of ModuleMetadata in
ModuleMetadataRepository.

Deployment unit status in ModuleMetadata is now final.

Simplified implementation of deployment unit status
retrieval.

Utility for reporting client requests from ZK log
Add SFTP source module

- Add module options and config
- Add tests
XD-1879 Add JdbcSink Test for InitializeDB=false.
XD-1877, XD-2245 refactored and enhanced gemfire module.xml and added Gemfire integration tests

Code polished based on code review comments

Renamed file with proper capitalization
Fixed case problem with GemFireServerSink
add sleep to scripts in spring-xd-extension-process to avoid stream closed errors in tests
XD-1876 Add test for #jsonPath with a filter

This is part of the effort to retire the script tests.
XD-2061 Add Redis sink module

 - Add Redis sink with the following options:
    - topic (a SpEL expression)
    - hostname, port and password
try synchronized on failing tests