support geo: URIs as a way to share location

[eighthave]

geo: URIs are an emerging standard way to share location information. It is fully supported on Android, with all map apps able to accept and properly respond to them. ChatSecure-android also now supports them (guardianproject/ChatSecureAndroid#610)

I'm not sure if iOS underneath already supports geo: URIs, if not, ChatSecure could easily convert them to https://www.google.com/maps/?ll=35.2342432,-120.4533453&z=8

http://maps.apple.com/?ll=35.2342432,-120.4533453&z=8 seems to the be Apple recommended way, but it is pretty crappy since it is only available via HTTP.

[eighthave]

From openstreetmap/openstreetmap-website#799 is some more info related to iOS:

Every map application seems to use an own url scheme on iOS:

• The Google maps uses comgooglemaps:// and comgooglemaps-x-callback.
• Apple maps supports but does not document maps:// and catches http://maps.apple.com

[mwlczk]

Hi, thx. For the great work with OMEMO, groupchat and push. This is a huge gain for security and usability.
Once the polish is finished, it would be so great to see this feature aswell.