Use device manager to add/remove all video providers dynamically, remove
v4l2 specific code.
Get the client proxy from subscribe instead of waiting for the
subscription callback. This way we can actually make an error on
failure.
Clean up the objects when the server disappears.
Remove subscription from the server, we don't need it. Install server
objects in bus_acquired.
Avoid using the autogenerated object manager because it does not
emit signals in the right context in all cases. Use our own proxy
and make our own proxy objects when they appear.
Make it possible to get a previously created proxy object or wait when
it is still being constructed.
Add introspect API
Move private things to private.h
Use custom main-context for the context, and ensure everything is called
from the custom main-context. does not work well with glib proxy signals
yet.
Work with custom mainloop in the gstreamer element.
