CDK-668: Update maven plugin to setup DefaultConfiguration.

Previously, properties set in the plugin's configuration were local and
the getDatasetRepository method had to use repository builders to use
the correct file system. This updates the method to create repository
URIs instead and changes the getConf method to update the default
Configuration.
The location isn't a folder that corresponds to the warehouse directory, it is the path used by both Hive and Kite that points to where the data is. Both call it location, so I think it's definitely the right thing to use in the single-dataset case. The repository's path is called a root because it defaults dataset locations based on the path it is given. In the case of a managed repository, there isn't a path and everything goes in the warehouse directory.