GEOMESA-233 adding scalding job to index attributes through geoserver UI

* new jobs module for m/r related code
* accumulo source/tap for scalding
This is running from GeoServer, so all the accumulo/etc jars are provided dependencies in the GeoServer lib folder.
I think I'll put the list of jars into a text file in the resources folder - that way it could be tweaked if necessary without rebuilding.