GUID and timestamp extract from ingress JSON dataset

Stores portal GUID and timestamp from JSON dataset into portals object
array
GPX export function added. GUID, lat, lng and timestamp into CSV export

New GPX export function.
Columns for GUID, latitude, longitude and timestamp added to CSV export
export all portals to GPX, KML, CSV

Added links at the top of the page to export all portals as GPX, KML or
CSV