Renamed to flatpak in git

[Alexander Larsson]

I just pushed the changes to git master to rename everything "flatpak".
This means the binary is now named "flatpak".

The following should keep working:
 * Anything installed with --user (we migrate ~/.local/share/xdg-app to
   ~/.local/share/flatpak). You can't go back though, the migration
   is one-shot.
 * Existing repositories. Nothing changed wrt the repository format.

However, the following is not compatible:
 * System installed apps/runtimes (/app
 * Bundle format (changed magic cookie)
 * binary changed name (xdg-app => flatpak, 
   xdg-app-builder => flatpak-builder)
 * flatpak-builder uses a subdirectory named
   ".flatpack-builder", not ".xdg-app-builder".
 * The bus name and interface name for the permission
   store is changed, it was in org.freedesktop.XdgApp, but is
   now in org.freedesktop.impl.portal.DesktopPortal.


Further is a list of things that has to be changed to sync with the
name change:

 * mailing list name
 * bugzilla component
 * git repo
 * tarball release location
 * Fix up gnome-shell to use the new dbus name for the permission store
 * Update shared-mime-info for new bundle format
 * Update the runtimes/apps git repos so we build with the new commands
   instead of the old ones.

-- 
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
 Alexander Larsson                                            Red Hat, Inc 
       alexl at redhat.com            alexander.larsson at gmail.com 
He's an uncontrollable flyboy rock star for the 21st century. She's a 
cold-hearted tempestuous opera singer in the witness protection program. 
They fight crime!