Update consolekit to 1.2.0.

• Rename consolekit to consolekit2 to reflect that consolekit2 is a new project, even if it the continuation of the old consolekit project.
• Expand pkg-descr with some background info.
• Add license
• ConsoleKit2 has been ported to GDbus, so dbus-glib is not anymore required
• Add GObject introspection support for desktops environment such Pantheon or Deepin.
• Thanks to Jesper Schmitz Mouridsen, Ben Woods and Olivier Duchateau for assisting with there versions of the port, suggesting changes and testing.

PR: 202269