XD-1972: Add ability to define nested jobs
JIRA: https://jira.spring.io/browse/XD-1972
* add suport for nested jobs
XD-1972: Made nested jobs a non-breaking change

This commit converts the logic of how a job is named so that if there is
more than one Job in the module's context, the one to be executed must
have the id "job".  If only one Job exists in the module's context, then
it can be any name.
XD-2231 Update batch configuration keys to be camel case
XD-1864 Paging support in the web UI

Handle none existing pages gracefully in `PagingUtility`

* Add tests for `PagingUtility`
* Raise a `PageNotFoundException` for non-existing pages
* Return a **404** HTTP status in case a `PageNotFoundException` is thrown

XD-1864 Add `angular-utils-pagination` dependency

XD-1864 Update CSS styling of Bootstrap pagination bar

XD-1864 Add paging support for UI list views

* Add pagination to Job Modules, Job Definitions, Stream Definitions
* Ensure filtering still works
* Ensure polling still works

XD-1864 Update E2E Tests

XD-1864 Add `Pageable` class

XD-1864 Code Review Changes

* Center Pagination

XD-1864 Code Review

* Fix test compilation issue
Fixed attribute nesting.
XD-2235 Allow 'security.basic.realm'

 - to control the security realm
Randomize props in BatchConfigurerIntegrationTests
XD-2247: Log version number in log files

Support for logging version number obtained from
"Implementation-Version" string in manifest file.
Version number is logged by adding "%v" to the
conversion pattern string.
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
XD-2151 Create the SSLContext early and cache it

Caches the SSLContext right after bean creation, preventing expensive operations such as SSL certificate parsing to take place more than once. The SSLEngine needs to be created per Netty Channel, as it is not thread-safe.