JobList low-level code relateod to primitive jobs now uses shared pointers instead of ByteStream refs talking to DEC
b/c same-node EM-PP communication now goes over a queue in DEC instead of a network hop.
PP now has a separate thread that processes the primitive job messages from that DEC queue.
operations + morsel size weight model to equally allocate CPU b/w parallel query morsels.
This patch delivers better parallel query timings distribution(timings graph resembles normal
distribution with a bigger left side thus more queries runs faster comparing with PrioThreadPool-based
single-node installation).
See changes in batchprimitiveprocessor-jl.h and comments in fair_threadpool.h for
important implementation details
PP now uses PriorityThreadPool that arbitrary picks another jobs pack
to run. This scheduling discipline tend to run portions of a single query
forcing other simultaneous queries to wait. In result parallel queries
timings variance is high. The FairThreadPool picks the job with the smallest
amount of work done so far(see the code for details)
