Add option to upload to other servers

Submitted by jeyca

Assigned to Jérôme Guelfucci

Link to original bug (#14421)

Description

currently there are options to immediately upload screenshots to imgur or or zimagez, but they both use trackers or one needs to register. It would be a big privacy improvement to have the chance uploading images to Framapic.org, where they will be stored encrypted, no trackers are used and you don't need to register.

In general it would be great to be able to integrate any custom server/apis.

Version: 1.8.2