Add instrospection of client and source-output.
Add properties to source-output and to CreateSourceOutput/Input
Add helper to fill properties of context.
Add client-name to pinossrc and pinossink
Improve test-subscribe to show all new introspection details.
Set the active device providers as a property on the daemon. In the
device monitor we can then obsolete the already monitored devices.
Copy all device properties to the source. Set the device class as
a property on the monitored devices.
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.
