PIG-3123: Simplify Logical Plans By Removing Unneccessary Identity Projections (njw45 via cheolsoo)


git-svn-id: https://svn.apache.org/repos/asf/pig/trunk@1508153 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/trunk' into trunk
Merge remote branch 'origin/trunk' into trunk-gd