Start replication to paired servers on desktopcouch startup

Exclusion list should be a MergeableSet listing database names.

Paired server record should define:
server: a server name or IP address (name for preference, .local names for machines on the lan)
oauth: {
  consumer_key: string,
  consumer_secret: string,
  token: string,
  token_secret: string
}
database_name_prefix: string, a prefix to add to DB names when replicating to this server

Paired server record should also contain

pull_from_server: true

if localhost is expected to do both push replication (as standard) to this server *and* pull replication *from* this server. If this entry is absent, do push replication to this server only.

Instead of "database_name_prefix", how about "database_name_format", so "prefix_%s_suffix" ?

Also, I'm wary of changing the name, if it's ever possible the far end will inject the new database name into our replication upstream somewhere.

pairing_identifier: str(uuid) (the primary identifier, as names collide, and addresses vary)
server: a server name or IP address (name for preference, .local names for machines on the lan)
oauth: {
  consumer_key: string,
  consumer_secret: string,
  token: string,
  token_secret: string
}
database_name_prefix: string, a prefix to add to DB names when replicating to this server

Remove database_name_prefix, and assume we always replicate to a database the same name on the remote end. (If this is a problem, for example if you have many users' databases on the server and two users may have databases with the same name, then have a proxy which redirects based on oauth token.)