Initial patch for review. Reverted 2745 as removing leading / is moved to PigContext itself. Easier to do that in PigContext.addScriptFile() than repeat it in each of the ScriptEngine implementations and PigServer. Changed the ScriptEngine.getScriptAsStream() to try all classloaders.
Working on writing a e2e test for this.
This patch does not address 2760. Trying to see if there is a easy way to accomodate that in this patch without impacting the changes for s3
PIG-2623. The easier thing would be to add two copies of the script file to the jar - one with absolute path and one relative path but it is not efficient.