Observable client-side preferences and configs

[lbwexler]

Its always been a little strange that preferences and configs are only updated on the client when the entire page is refreshed. We think it would be very natural to push or poll for updates, and make the collections observable on the client.

Just doing so will not automatically make all hoist and app code reactive to these, but it is the first step, and we think its a capability that could be gradually exercised if we made it available.

[amcclain]

For configs, we discussed admin option to push changes, rather than pushing after each modification or a client-side refresh. Would allow admin to change several configs, validate, then push to clients. Also discussed how this puts an extra burden on developers to document if configs would be read again.

[amcclain]

For preferences, discussed how making them observable (within a single client) could save some boilerplate code and is a clear win, but refreshing might or might not be worth implementing.

But reloading would get you sync across multiple clients with the same user, potentially avoiding some confusion over e.g. saved dash layouts or favorites not syncing