CDK-619: Implemented read/write support for Pig

     * The patch still needs to move the pig dependencies under
       dependency management in the parent pom.
     * This needs more tests, in particular on error handling.
Oh my, this is super sketchy. Let me see if I can explain what needs to happen and if you have a good suggestion for a less hacky solution. So, despite the fact that Pig delegates the location you specify in a LOAD/STORE statement to the LoadFunc/StoreFunc specified, it always turns the location into a Path() object. Path() will throw an exception if the URI it gets is not an absolute URI.

So, we need to trick Path() by modifying the URI in relativeToAbsolutePath() and relToAbsPathForStoreLocation() to have a / after the scheme (dataset or view). This method then fixes that before passing the URI to the Datasets method.

Whatever we do won't be pretty, but I'm sure we can do better than what I already put in :)