Use the more generic get_stage_results instead of get_map_results.
Change the HTTP API to use stageresults instead of mapresults.

Now the client can request for the result of any arbitrary stage and not only
the map stage.
Replace the mapreusults command with stageresults.

Issueing stageresults without any arguments will default to the map stage and
will return the resuls of the map stage.
Merge pull request #425 from pooya/shayan/stage_results

Shayan/stage results