[SPARK-11179] [SQL] Push filters through aggregate

Push conjunctive predicates though Aggregate operators when their references are a subset of the groupingExpressions.

Query plan before optimisation :-
Filter ((c#138L = 2) && (a#0 = 3))
 Aggregate [a#0], [a#0,count(b#1) AS c#138L]
  Project [a#0,b#1]
   LocalRelation [a#0,b#1,c#2]

Query plan after optimisation :-
Filter (c#138L = 2)
 Aggregate [a#0], [a#0,count(b#1) AS c#138L]
  Filter (a#0 = 3)
   Project [a#0,b#1]
    LocalRelation [a#0,b#1,c#2]

Author: nitin goyal <nitin.goyal@guavus.com>
Author: nitin.goyal <nitin.goyal@guavus.com>

Closes #9167 from nitin2goyal/master.