Add a fallback handler for the geo: URI scheme

Technically this is a tiny helper program that parses geo: URIs and translates them to e.g. OSM website URLs. The URL patterns are provided as arguments, so we can support arbitrary many services that way. Support for wheelmap.org is included to demonstrate this, proprietary services like Google Maps can be added in the same way if desired.

The goal of this is to allow applications to rely on geo: URIs to be handled unconditionally, independent of whether Marble or another map application is installed. This would allow a number of applications to drop duplicated platform-specific custom code, such as KAddressBook, KMail, Kalendar and Itinerary.

The second piece for this is the ability to select the preferred geo: URI handler in systemsettings "Default Applications" module, which still has to be implemented.