* Ported Fault Tolerant AbstractHDFSExactlyOnceWriter operator from guava poc
     * Added counters to track total time and bytes written.
     * refactored HdfsExactlyOnceOutputOperator to use AbstractHDFSExactlyOnceWriter
     * deprecated AbstractHdfsFileOutputOperator
     * removed obsolete AbstractHdfsOutputOperator
     * removed obsolete AbstractHdfsRollingFileOutputOperator
     * removed obsolete HdfsOutputTupleInterface
     * removed unused benchmark HDFSBothInputOutputOperatorsBenchmark
     * modified HDFSOutputOperatorBenchmark to use fault tolerant writer
     * Updated Fraud detection demo to use fault tolerant writer
     * Updated map reduce demo to use fault tolerant writer
Fixed license header
 - Made rolling property of ExactlyOnceWriter set by specifying a maximum length
 - Updated tests and demos with change
 - Misc corrections to exactly once operator
  * Removed Exactly Once from class names
  * Made AbstractFSWriter operate in Exactly Once, At Least Once and At Most Once operating modes.
  * Provided a default implementation of the convert method which throws an Unsupported operation exception.
  * Moved Random Word Generator into test bench.
  * Added many more unit tests. Fixed newly found bugs.
  * Additional small misc corrections.
* Removed Exactly Once from class names
  * Made AbstractFSWriter operate in Exactly Once, At Least Once and At Most Once operating modes.
  * Provided a default implementation of the convert method which throws an Unsupported operation exception.
  * Moved Random Word Generator into test bench.
  * Added many more unit tests. Fixed newly found bugs.
  * Additional small misc corrections.
Merge branch 'dt-dev' into MLHR-1415_pull
  * Removed unnecessary IOTestHelper
  * Added flag to cleanUpDuplicates on operator recovery for AbstractFSWriter
  * Removed unnecessary override of convert method for test subclasses of AbstractFSWriter
Updated benchmark results.
  * changes UnsupportedOperationException to assert.
 * Removed spurious override of convert method in map reduce demo
 * Throw exception and gave appropriate error message when closing resources in teardown for
   input and ouput operators
 * Handled edge cases for rolling files
 * Changed append property to define how files are treated when discovered by the operator. If
   the operator finds a previously unseen file and append is true, then that file is appended
   to. If the operator finds a previously unseen file and append is false, then that file is
   overwritten.
  * Fixed tests for single file writer.
 * Fixed test and imports
  * Fixed FSWindowWriter
  * Fixed improved tests for FSWindowWriter.
  * Made FSWindowWriter abstract
  * Fixed warning
few corrections
Merge branch 'ilooner-MLHR-1415_pull' into dt-dev