(PIG-2597) Move Grunt from JavaCC to ANTLR

by Kyungho Jeon for Apache Software Foundation

Apache Pig a platform for analyzing large scale data sets using high-level data flow language. Currently Pig utilizes two frameworks, JavaCC and ANTLR for generating language processors. In this Google Summer of Code project, I will reimplement GruntParser using ANTLR and merge it QueryParser. Removing GruntParser's dependency on JavaCC will help Apache Pig project keep clean, easy to maintain codebase and continue to be improved by many contributors.