Fix argument handling in irsa.Irsa.query_region

* The default spatial query type (`spatial='cone'`) was incorrectly
  capitalized (should be `spatial='Cone'`), so that using the default
  always caused an empty result set.
* An 'else' clause now catches completely unrecognized spaital query
  types.
* Coordinates are now formatted in a way that is recognized by the Gator
  service.