XD-1306

Created spring-xd-extension-batch project and moved RemoteFilePartitioner and RemoteFileToHadoopTasklet from spring-xd-dirt to the new project.  Removed spring-integration-file and spring-integration-ftp from the dirt dependencies, and moved BusTestUtils to spring-xd-test, since now shared by spring-xd-dirt and spring-xd-extension-batch. 

To avoid installing every hadoop distribution ftphdfs/lib, introduced https://github.com/spring-projects/gradle-plugins/blob/master/propdeps-plugin to support provided dependencies.  This required an update to gradle 1.12, which has some known issues with intellij.  The ftphdfs job deploys successfully, but a full integration test for that job has not been run yet.