This essentially adds an accessor for the MimeType field in desktop files,
to retrieve the list of all mime types supported by an application.
The interface though is part of GAppInfo, so it could be implemented
in the future by other backends.
https://bugzilla.gnome.org/show_bug.cgi?id=674111
This adds a GApplication object to GIO, which is the core of
an application support class, supporting
- uniqueness
- exporting actions (simple scripting)
- standard actions (quit, activate)
The implementation for Linux uses D-Bus, takes a name on the
session bus, and exports a org.gtk.Application interface.
Implementations for Win32 and OS X are still missing.
