plugin: refactor the initialization code.
plugin: refactor the initialization code.

Remove references to global python objects from the initialization code. This
makes it possible to avoid linking to libpython.

alessandrod/gst-python,pexip/gst-python,pexip/gst-python,freedesktop-unofficial-mirror/gstreamer__gst-python,alessandrod/gst-python,alessandrod/gst-python,lubosz/gst-python,freedesktop-unofficial-mirror/gstreamer-sdk__gst-python,GStreamer/gst-python,GStreamer/gst-python,freedesktop-unofficial-mirror/gstreamer-sdk__gst-python,pexip/gst-python,freedesktop-unofficial-mirror/gstreamer-sdk__gst-python,lubosz/gst-python,freedesktop-unofficial-mirror/gstreamer__gst-python,GStreamer/gst-python,lubosz/gst-python,freedesktop-unofficial-mirror/gstreamer-sdk__gst-python,freedesktop-unofficial-mirror/gstreamer__gst-python