Rename the payloader and depayloader to pinospay/pinosdepay because they
now store data in a pinos specific format.
Subclass GstElement because they are not real transform elements.
Rework/remove some buffer functions that are not used by some more
performant ones.
Split setup of pipeline and state change to inspect the pipeline formats
and properties. Pass the device monitor caps to the gstreamer source so
that we don't have to query that again.
Work on adding time provider to the sender pipeline. Send the port and
address to the client in the source-output object properties.
Improve properties API and add some more docs.
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.
