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.
What does this do? The result is passed directly into `Datasets.load` above so it should produce a dataset or view URI. But it appears to check if the URI is absolute (assuming that it has a scheme) and remove the beginning '/' if so?