Starting a revised version of Pregel
adding iteration number to context
Simplifying pregel api and applying to pagerank.
further simplifying API
Fixing unit tests.
removing extraneous files.
minor cleanups
adding breaking test to tests
removing context and passing activeness directly through the vertex property.  This addresses the issue where byte-code inspection would always force a 3-way join.
Adding PregelVertex type which encapsulates the vertex and its activeness.
Improving documentation
Merge commit 'refs/pull/1217/head' of github.com:apache/spark into GraphXALS
Make ALS work with new Pregel (still fails tests)