Fix csv reblock multiple inputs w/ same name (new cse persistent reads)
Fix csv reblock multiple inputs w/ same name (new cse persistent reads)

If the same input file is passed to two different reads, until now, we
redundantly read and reblocked both inputs. This lead to specific
anomalies when two csv inputs with the same file name were piggybacked
into a single csvreblock job because unknown size handling and row id
handling are done wrt filenames. Since redundant reads are anyway highly
undesirable, we now perform common subexpression elimination also for
persistent reads, which merges reads if possible. In combination with
other IPA rewrites, we are even able to propagate this information over
the entire program allowing various simplifications. 
dusenberrymw/systemml,asurve/arvind-sysml2,dusenberrymw/incubator-systemml,nakul02/systemml,asurve/incubator-systemml,akchinSTC/systemml,asurve/systemml,deroneriksson/incubator-systemml,gweidner/systemml,gweidner/systemml,sandeep-n/incubator-systemml,niketanpansare/incubator-systemml,iyounus/incubator-systemml,deroneriksson/incubator-systemml,dhutchis/systemml,dusenberrymw/incubator-systemml,akchinSTC/systemml,nakul02/incubator-systemml,nakul02/incubator-systemml,iyounus/incubator-systemml,akchinSTC/systemml,asurve/arvind-sysml2,gweidner/incubator-systemml,dusenberrymw/systemml,nakul02/systemml,niketanpansare/systemml,gweidner/incubator-systemml,iyounus/incubator-systemml,akchinSTC/systemml,apache/incubator-systemml,fschueler/incubator-systemml,asurve/arvind-sysml2,niketanpansare/systemml,nakul02/incubator-systemml,deroneriksson/systemml,nakul02/systemml,dusenberrymw/systemml,asurve/incubator-systemml,apache/incubator-systemml,gweidner/systemml,niketanpansare/incubator-systemml,gweidner/incubator-systemml,gweidner/systemml,gweidner/incubator-systemml,dusenberrymw/systemml,iyounus/incubator-systemml,nakul02/incubator-systemml,nakul02/incubator-systemml,asurve/systemml,dusenberrymw/incubator-systemml,gweidner/incubator-systemml,dhutchis/systemml,gweidner/systemml,nakul02/systemml,deroneriksson/systemml,dusenberrymw/systemml,fschueler/incubator-systemml,dhutchis/systemml,deroneriksson/incubator-systemml,gweidner/incubator-systemml,deroneriksson/systemml,akchinSTC/systemml,sandeep-n/incubator-systemml,deroneriksson/incubator-systemml,sandeep-n/incubator-systemml,apache/incubator-systemml,asurve/systemml,asurve/arvind-sysml2,asurve/systemml,iyounus/incubator-systemml,asurve/arvind-sysml2,apache/incubator-systemml,dusenberrymw/incubator-systemml,dusenberrymw/incubator-systemml,niketanpansare/incubator-systemml,nakul02/systemml,deroneriksson/systemml,niketanpansare/systemml,deroneriksson/systemml,nakul02/systemml,niketanpansare/incubator-systemml,Wenpei/incubator-systemml,fschueler/incubator-systemml,iyounus/incubator-systemml,Wenpei/incubator-systemml,dusenberrymw/incubator-systemml,deroneriksson/incubator-systemml,nakul02/incubator-systemml,gweidner/systemml,asurve/incubator-systemml,sandeep-n/incubator-systemml,dusenberrymw/systemml,asurve/incubator-systemml,niketanpansare/systemml,asurve/systemml,asurve/arvind-sysml2,fschueler/incubator-systemml,niketanpansare/systemml,asurve/incubator-systemml,niketanpansare/systemml,asurve/incubator-systemml,Wenpei/incubator-systemml,akchinSTC/systemml,deroneriksson/incubator-systemml,Wenpei/incubator-systemml,dhutchis/systemml,apache/incubator-systemml,deroneriksson/systemml,dhutchis/systemml,dhutchis/systemml,apache/incubator-systemml,asurve/systemml