XD-1104: Add tests for jdbc sink module and fix bugs
XD-1162 Adding check for existing value with underscore column name
Fix xd-config.yml

- Added the separator "---" between Redis
and RabbitMQ properties
XD-1356 Adding missing build script entries for 'hdp20'

- Adding missing placeholder for distro directory
XD-1349 Making HDFS configurable via application.yml

- Adding defaults in application.yml

- Using config/hadoop.properties for additional config options
XD-1105: Simple mqtt integration test

Add MqttTestSupport rule.

Note that none of the RabbitSingleNodeStreamDeploymentIntegrationTests
will run if matt is not available as this stands. However it is trivial
to enable the matt plugin in rabbit so this is cleaner than splitting
out a separate rabbit integration tests class for the matt test.
Application now uses singlenode attr in artifact.

Updated formatting for README.md
XD-1367: Remove commons-logging jars from XD distro.

The main lib directory has slf4j jars including jcl-over-slf4j
so we don't need commons-logging. This change excludes them from
the copy of spring-xd-dirt to the final distro. Otherwise we end up
with 27 copies of the jar in the various module and extension
subdirectories.
XD-1350: Remove enums as option coercion mechanism
Made includes/excludes more explicit