Fix userStore attempting to fetch the users list when it's either not
logged in or not allowed to fetch the users, causing the schedule page
to not render.
Move the logic that converts the EntityClass of a map to a string and
then back into the class to the payload plugin in order to avoid a
circular dependency where the ClientMap needs to know the entity classes
and the entity classes needs to know the ClientMap.
The only place that doesn't know the type of the entities stored in the
client map is the payload reviver, so it makes sense to keep this logic
contained to the payload plugin.
Rename accounts to users to be consistent with the new naming scheme
where account only referes to the logged in user of the session and
implement live updates of users via a user store which listens for
updates from the event stream.
