Decide how to integrate scheduler info into CLI and job tracker web page

We need a way for job schedulers such as HADOOP-3445 and HADOOP-3476 to provide info to display on the JobTracker web interface and in the CLI. The main things needed seem to be:

• A way for schedulers to provide info to show in a column on the web UI and in the CLI - something as simple as a single string, or a map<string, int> for multiple parameters.
• Some sorting order for jobs - maybe a method to sort a list of jobs.

Let's figure out what the best way to do this is and implement it in the existing schedulers.

My first-order proposal at an API: Augment the TaskScheduler with

• public Map<String, String> getSchedulingInfo(JobInProgress job) – returns key-value pairs which are displayed in columns on the web UI or the CLI for the list of jobs.
• public Map<String, String> getSchedulingInfo(String queue) – returns key-value pairs which are displayed in columns on the web UI or the CLI for the list of queues.
• public Collection<JobInProgress> getJobs(String queueName) – returns the list of jobs in a given queue, sorted by a scheduler-specific order (the order it wants to run them in / schedule the next task in / etc).
• public List<String> getQueues();