XD-1032 First stage for converting Hadoop module to isolated classloader...

... scheme

- changing spring-data-hadoop version to 2.0.0.BUILD-SNAPSHOT so we can include
   the new spring-data-hadoop-store sub-project

- removing spring-xd-extension-hdfs replacing with spring-data-hadoop-store

- this is the first step in converting the spring-xd-hadoop module to remove hadoop
  dependencies from the spring-xd-dirt classpath and instead using isolated classloader
  scheme for any hadoop modules