Delete GTFS data when 'delete' button clicked.

Also zoom to world extent when no data loaded, or after data deletion.
Add error handling for GTFS deletion; tidying
Merge pull request #48 from flibbertigibbet/feature/delete-gtfs

Delete GTFS data when 'delete' button clicked.
Fix numStopsPerMode indicator
Comment out avgTransitLengthPermMode tests
Merge pull request #49 from WorldBank-Transport/feature/fix-num-stops-per-mode

Fix numStopsPerMode indicator
Increases the Geotrellis timeout to 2 minutes.

So far, the longest any GTFS feed has taken to process is about 30
seconds.
Idle-timeout needs to be greater than request-timeout.
Merge pull request #51 from WorldBank-Transport/feature/increase-geotrellis-timeout

Increases the Geotrellis timeout to 2 minutes.