Added join and aggregateUsingIndex to VertexPartition.
More, bigger cleaning for better encapsulation of VertexSetRDD and VertexPartition. This is work in progress as stuff doesn't really run.
Added a log4j properties file for graphx unit tests.
Fix join error by caching vTable in mapReduceTriplets
Fix VertexSetRDD test by enabling index reuse
Enable joining arbitrary VertexPartitions (with different indexes).
Merge branch 'clean1' of github.com:amplab/graphx into clean1
Revert "Fix join error by caching vTable in mapReduceTriplets"

This reverts commit dee1318d3d4e37489dc2b0bb373857cc13b4d533, which is
unnecessary due to 7528e6d5f15fd0e01a206f60a6db218858cac4d3.
Minor update to tests.
Merge branch 'clean1' of github.com:amplab/graphx into clean1
Added an optimized count to VertexSetRDD.
Made all VertexPartition internal data structures private.
Merge branch 'subgraph-test' of github.com:ankurdave/graphx into clean1

Conflicts:
	graph/src/main/scala/org/apache/spark/graph/impl/VertexPartition.scala
Merged Ankur's pull request #80 and fixed subgraph.
Created EdgeRDD.
Removed PartitionStrategy from GraphImpl.
Memoize preferred locations in ZippedPartitionsBaseRDD so preferred location computation doesn't lead to exponential explosion.
Created an algorithms package and put all algorithms there.
Use specialized shuffler for aggregation.
Merge pull request #81 from amplab/clean1

Codebase refactoring