Reader batch support

Producer.cc

TestThrottleReadClient.cc

src/AbstractLog.cc

src/AbstractLog.h

src/InfRcTransport.cc

src/Logger.cc

src/MakefragTest

src/MasterService.cc

src/MultiLog.cc

src/MultiLog.h

src/MultiReadGroup.cc

src/RamCloud.h

src/Segment.cc

src/SegmentIterator.cc

src/SegmentIterator.h

src/WireFormat.h