WIP: Vanchi/better presence

:construction: 
* Creates a Presence Sentry (one per server instance) which can send/listen to server keep-alive and notify if a server is done.
* Eliminates need for Local/Remote managers
* Disconnect queueing is a simple timeout

/cc @zendesk/zendesk-radar


### Steps to merge
 - [ ] :+1: of the team
 - [ ] Fix/rewrite failing tests
 - [ ] Create multiple server tests (better remote tests)

### References
 - Jira link: https://zendesk.atlassian.net/browse/RADAR-306

### Risks
 - Presence does not work as expected.