Add jasmine specs for MetadataExtent class
(cherry picked from commit 799f4c82ec5e2a4fce18fe809366f90ece7ed9af)
Renamed ResultsStore to GeoNetworkResultsStore as per review
Add guard code around call to setCenter of Map

Some of the layers do not generate a bounding polygon and calling setCenter on the map in those
result rows causes JS errors.