Significant updates to tasks, server/worker interaction, task queuing, and document processing.
  Task:
  - Added a success attribute to distinguish tasks which were completed but encountered some error condition.  In case of task failure, the server may decide how to proceed.
  - Standardized logging output via convenience method provided by the abstract Task base class.  Subclasses may log additional information as a further log message.
  - Task objects are now identified by a randomly generated UUID.
  - Task objects are now tagged with the ID of the worker which processed them.
  TaskServer:
  - Refactored task queuing logic from the TaskServer into the TaskQueue class which now provides a central point of management for queued tasks, continuation tasks, and a delayed queue for retrying dropped tasks.
  - Tasks are now resolved when returned to the server.  Unresolved tasks are returned to the task queue after some timeout (configured by task.retry.seconds).
  - Moved RMI registry/export logic into TaskServer.start() from main().
  - Standardized logging output via convenience method.
  ParserTask:
  - The ParserTask now processes the document text passed to it from the server rather than attempting to read it from disk (since the worker will not have access to the data volume).
  - Updated paths used by the ParserTask to determine the appropriate news outlet for a document.
  - Added support for parsing XML from the Baltimore Sun.
  - Read in XML documents as UTF-8.
  CoreNlpTask:
  - Wrapped the StanfordCoreNLP annotator pipeline so that there is a place to consolidate pipeline utility methods (timing instrumentation, so far).
  - Set the maximum parser token size (configured using corenlp.parse.maxlen) to avoid out of memory conditions.  When the parse fails, dependencies are not persisted to the data store.
  Miscellaneous:
  - Added collection of various statistics (token counts, annotator timing) to document entities stored in a simple key/value map attribute which can be used at any level in the document.
  - Updated TODO.txt.