endpoint.description is now the user-friendly string
we want the endpoint name to be machine-friendly because it's
the identifier that we store in m-session-settings

this allows the created nodes to be able to set their "device.id"
property correctly

- fall back to the default logic if node.target is set but it doesn't exist
- use the default endpoint if it is within the [target-endpoint] matches;
  this way we can use a config file to override just the stream name,
  for instance, while still respecting the default endpoint
- prefer use of the lookup methods instead of manual iterations

previously the default endpoint was not respected because our config
files have a [target-endpoint] table..

they are not useful anymore because we hijack priv->info from the
impl subclass, so that it points to the impl info struct,
and therefore the base implementations work just fine

m-device-activation: use wp_core_timeout_add_closure instead of wp_core_timeout_add in reserve node API

This allows dbus requests to be done inside the task callback

This reverts commit 917a019b.

so that we can filter proxies by id on object managers

- make it a GObject so that it can emit its own signals
and so that it can be shared between multiple proxies
- share the WpProps instance between endpoints, endpoint-streams
and their underlying nodes
- introduce the concept of the caching mode that redirects _set
to _set_param of the proxy that actually has the props; this allows
shared WpProps to actually set changes on the correct proxy
in a transparent way
- change methods to consume the ref of the pod and reflect that
also on wp_proxy_set_prop()
- refactor the export process on endpoints & endpoint-streams
so that they always get all the required features (info, props, bound)
and make it async so that we can take time to prepare the underlying
node to have FEATURE_PROPS
- update the props & endpoint unit tests, bringing back all the
checks that the endpoint unit test used to have

m-config-static-nodes: remove unneeded 'conected' callback and create static nodes when the plugin is activated