Fix setupUI dependency tasks

 - Always `clean` spring-xd-ui project before building
 - Always run `build` after `grunt_build` in setupUI
XD-2069 Enable HTTP source debugging

- Add logging statements at DEBUG level in NettyHttpInboundChannelAdapter
- Add a LoggingHandler to the processing pipeline if DEBUG is enabled for log4j.logger.org.jboss.netty.handler.logging.LoggingHandler
XD-2226 ZooKeeper namespace is now configurable

The zk.namespace property can be set in servers.yml (default is "xd").

Also removed the buildWithNamespace() methods from Path implementations.

removed buildWithNamespace links from javadoc

added zk namespace to application.yml
Log ZK namespace
XD-2060: Add jdbc source

 - Use factored out datasource in jdbc sink as well

 - Add transaction manager for module dadasource