XD-1332 XD Int Test pauses should be configurable

Exposed properties in the build.gradle

Had to add support for relative directories for the CI Build

Updated documentation

Updated Documentation
XD-1309: Skip option validation when doing completion
XD-1122 Add mgmtPort option

Adds an option to set the port on which Spring Boot's management
server listens. 

- Added `mgmtPort` as a CommonOption (for both admin/container)
- The management port can also be set via `XD_MGMT_PORT` as an environment
  variable property
- By default, the mangement port uses admin/container server port in
  admin/container servers respectively.
XD-1021,1037,1277,1039 Fix composed module options

Implement module options advertising and dispatching for composed
modules.
XD-647 Refactor message converters to implement MessageConverter interface

XD-647 merged ModuleTypeConversionPlugin

XD-647 Http source emits byte[] by default

XD-647 General cleanup, added custom converters hook

XD-647 Revert to http source emitting String by default, and Javadoc

Fix generics warnings

Bump groovy version
@Ignore a failing test for now pending investigation
XD-1321 XD-1322 Creating shell scripts and support classes to start XD on YARN

- Adding new spring-xd-<version>-yarn.zip file containing spring-xd-yarn zip and
  client and appmaster jars along with customization files and scripts

- Adding xd-admin and xd-container scripts for YARN

- Adding YARN Client and Appmaster implementations

- Removing directory paths from xd-yarn zip distribution

- New application.properties file can be used to override config options
XD-1291 Graceful container shutdown

- When the container shuts down, there are following application
contexts:
 - (1) ParentConfiguration global context
 - (2) LauncherApplication context whose parent is (1)
 - (3) Common context (from module common)
 - (4) Deployed modules contexts whose parent is (3)

With Boot RC3, the shutdown hook is registered only on (1)
and all the child contexts are subsequently closed using
ParentContextCloserApplicationListener.

This PR addresses the order in which the modules contexts are
closed by making sure the consumer modules (sink/processor) get
closed before the producer modules (if all are deployed inside
a same container).

- ModuleDeployer, during its destroy() will only publish the module
undeployment events as the modules contexts and the common context are closed
appropriately before the ModuleDeployer is destroyed.
XD-1291 Change precedence order

- The producer modules context should be closed before
the consumer modules context.