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

Still TODO - 
* create ticket for the TODO in the code
* error handling in UI for failed m/r jobs
* unit tests

i think i was thinking that if the seq was empty then it would never get instantiated... value makes more sense since in the delete case it won't ever get instantiated. should i change cf to not be lazy?