add mask operation to Graph
add filter operation to GraphOps
add a predicate to GraphLab to indicate active vertices at start
vertex should be inactive if no vertices scatter to it
Add standalone PageRank using only GraphX operators
Test standalone PageRank
Use standalone PageRank in Analytics
Remove static Pregel; take maxIters in dynamic Pregel
Merge pull request #99 from ankurdave/only-dynamic-pregel

Remove static Pregel; take maxIterations in dynamic Pregel
Merge pull request #91 from amplab/standalone-pagerank

Standalone PageRank
Load edges in columnar format

In GraphLoader.edgeListFile, load edges directly into EdgePartitions,
avoiding repartitioning.
Don't partition edges by default; refactor

Instead, expose Graph.partitionBy(PartitionStrategy).
Fix argument bug and closure capture
Clean up imports in EdgeRDD
Remove calls to ClosureCleaner in GraphX

All Spark RDD methods already clean closures so we don't need to.
Incremental view maintenance for all graph ops

All GraphImpl operations now support incremental maintenance of the
replicated vertex view by reusing vTableReplicated whenever
possible. This has two consequences:

- This is not confined to the deltaJoinVertices operator anymore,
  so we rename it to the more intuitive "updateVertices" instead.

- This enables mrTriplets to support skipStale.
Don't expose {src,dst}Mask in EdgeTriplet

Exposing this information is not necessary due to the addition of
skipStale.
Fix bug in mapVertices and outerJoinVertices
Finish up 49f7fc5ed2edd42b118182438d84ed7d4e7d521f
Fix bug in interaction of incr. view maint., skipStale, and join rewrite