Dispatch unsupported URIs to native apps on FreeDesktop.Org-compliant desktops

Fix defaults for XDG environment variables.

Draft logic for looking apps to dispatch MIMEtypes & URI schemes to on XDG platforms

Reverse locale reformatting for XDG config localized lookup.

Implement lookups of ini-file keys.

Improve error reporting & it's localization

Draft parser for FreeDesktop.Org config files.

This'll be used for dispatching URLs to be opened in external apps.

Add documentation, minor exported API adjustments.

Add Accept-Language support on UNIX systems.

Add Accept header support, remove cookies support

Extract URL resolver from Rhapsode

Each URI scheme can be turned on and off at build-time,
which has the side-effect of clearly labelling the code.