Server can pass information like an auth token to the client

#421 (closed) adds a "promisor-remote" capability so that client and server can exchange information and decide about which promisor remote the client can use.

So when #421 (closed) will be merged upstream, we will be able to use the "promisor-remote" capability to pass more information like an auth token and perhaps a filter too from the server to the client.

This is just about passing information (an auth token and a filter) from the server to the client through the "promisor-remote" capability. #623 is about actually storing and using that information on the client side (for other things than deciding if the client accepts a promisor remote).