(Graphx) Upstream necessary changes to graphx

[benmccann]

I'd like to make any changes necessary to graphx to use the upstream library. This repo is still on graphx 1.4 I believe and so we're not getting any of the graphx bug fixes.

I sent #56 and #57 to reduce the diff between graphx2 and upstream

I sent apache/spark#14291 to upstream addition of a new method

Changes left:

• GraphImpl.fromEdgeRDD visibility
• RoutingTablePartition.routingTable visibility
• Immutability in EdgePartition
• Can you explain why this change in GraphImpl was necessary?

[bhoppi]

Thanks mate!
The change is not that necessary. I just want to reduce an unneeded rdd.mapPartitions operation :-).
Because the only thing that GraphImpl.apply (line 341-354) is more than GraphImpl.fromExistingRDDs is that GraphImpl.apply calls EdgePartition.withoutVertexAttributes to generate a new empty vertex attributes array which will not be used at all.