gvariant.c: Elaborate on GVariant concept and its use
gvariant.c: Elaborate on GVariant concept and its use

Inserts a paragraph in the start of the description
explaining briefly the concept of GVariant as a
variant datatypes using examples and explaining
a few use cases where GVariant can be useful.

https://bugzilla.gnome.org/show_bug.cgi?id=748806

johne53/MB3Glib,johne53/MB3Glib,MathieuDuponchelle/glib,endlessm/glib,endlessm/glib,johne53/MB3Glib,MathieuDuponchelle/glib,endlessm/glib,MathieuDuponchelle/glib,endlessm/glib,johne53/MB3Glib,MathieuDuponchelle/glib,johne53/MB3Glib,johne53/MB3Glib,endlessm/glib,MathieuDuponchelle/glib