PIG: Move Grunt from Javacc to ANTRL

by Boski Shah for Apache Software Foundation

At the end of the program, I will deliver a patch with following set of changes. 1) Refactored Grunt parser code to use ANTRL instead of javacc. 2) Updated unit tests and e2e tests to accommodate above changes. 3) Build script changes to remove javacc parser generator code and replace it with ANTRL codegen. 4) Remove pig’s dependency on javacc library as it would not be used anymore