Ensure DSpace Replication Task Suite 1.x uses DuraCloud 2.1.2 and compiles for Java 6

This resolves an issue in RTS version 1.0 and 1.1.  Both of them were using a later version of DuraCloud API which required Java 7.  However, DSpace 1.8.x needs Java 6.

This pull request fixes errors like this one (which essentially said that DuraCloud required Java 7, which was unsupported):

    Exception: org/duracloud/error/ContentStoreException : Unsupported major.minor version 51.0
    java.lang.UnsupportedClassVersionError: org/duracloud/error/ContentStoreException : Unsupported major.minor version 51.0