CDK-453: Update MR configuration for Dataset URIs

These changes update the MR configuration API to use Dataset URIs and address the confusion raised on [CDK-453](https://issues.cloudera.org/browse/CDK-453). This commit changes the input and output formats to use dataset URIs rather than a repository URI and a dataset name. This also works with view URIs.

The configuration API has been changed to use config builders. For example,
```java
DatasetKeyInputFormat.configure(job).readFrom("dataset:hdfs:/datasets/myDataset");
DatasetKeyOutputFormat.configure(getConf()).writeTo(events.fromAfter("timestamp", startTime));
```

Crunch has been updated internally, but its API is unchanged.

This also fixes the bug when a Dataset is passed to `setView`.
DatasetKeyInputFormat is a part of the public API, so we can't just remove these constants (or static setters).