Fix vhost property of rabbit source/sink

Updated the property to use 'vhost' as in RabbitSourceOptionMetaData
and keep it the same for rabbit sink as well
Revert @PropertSource at MqttSourceOptions

- Added the placeholder properties back to source mqtt.xml
- Removed the bean validation constraints from MqttSourceOptionsMetaData
XD-1184 Fix IntegrationMBeanExporter name

- Added separate bean name for Admin, Launcher and
  ParentConfiguration's IntegrationMBeanExporter
XD-1191 Modifying JDBC sink configuration

- changing default for 'initializeDatabase' to false
  (this was the original value - used to be overridden in jdbc.properties)

- moving some default values back to xml file from options properties file
  so we can override them in the jdbc.properties file

- leaving initializeDatabase commented out in jdbc.properties since we are
  now using the existing batch database by default instead of a temporary
  in-memory db

- modifying test script to reflect change of default value
Updated the version number for the splunk source.
Remove 'columns' option in second jdbchdfs test

This isn't required when supplying the SQL directly.
XD-1178 Make avro sink options consistent with hdfs

Additional changes for this merge:
  - options.batchSize.description changed
  - timeoutOnIdle set to true for SimpleMessageStore

Squashed commit of the following:

    XD-1178 Make avro sink options consistent with hdfs
    - adding avro.properties with default values

    XD-1178 Make avro sink options consistent with hdfs
    - changing basePath to directory

    XD-1178 Make avro sink options consistent with hdfs
    - provide temporary custom implementation for DatasetTemplate
      to allow for null values in POJOs written (SHDP-245)
    - fixing avro sink expiration of groups
XD-797 Fix Package Tangle Introduced by XD-790

In *spring-xd-module*:

* Add `core` and `support` package
* Move Module and Plugin classes to `core` package
* Move `BeanDefinitionAddingPostProcessor` and `ParentLastURLClassLoader` to `support` package
* Move `DateTrigger` to `support` package and remove `util` package

Jira: https://jira.springsource.org/browse/XD-797

XD-797 Code Review Change
Fix FVC shell command for equal counts