Change BlockId filename to name + rest of Patrick's comments

...ava/org/apache/spark/network/netty/FileServerHandler.java

...main/scala/org/apache/spark/broadcast/HttpBroadcast.scala

...ain/scala/org/apache/spark/network/netty/FileHeader.scala

.../scala/org/apache/spark/network/netty/ShuffleCopier.scala

.../scala/org/apache/spark/network/netty/ShuffleSender.scala

core/src/main/scala/org/apache/spark/storage/BlockId.scala

...scala/org/apache/spark/storage/BlockManagerMessages.scala

...rc/main/scala/org/apache/spark/storage/BlockMessage.scala

core/src/main/scala/org/apache/spark/storage/DiskStore.scala

.../src/main/scala/org/apache/spark/ui/storage/RDDPage.scala

...rc/test/scala/org/apache/spark/storage/BlockIdSuite.scala