- added EventCenter for receiving events from other modules
  and dispatching them to subscribers using server-sent events
- added events panel in UI, in dashboard page
- added entity links component in UI for presenting in UI entities
  link machine or app as an exposed box with link
- in Rakefile task serve_ui is changed: now it only builds UI,
  and UI is served by stork server over 8080 port and not using
  angular cli server by 4200 port (this is caused by not working
  SSE in angular cli proxy)
- added submitting events in several places

Per review comments.

Per review comments.

Added hostname as a supported field, per review comments. Also, edited the
existing text slightly.

The example host_cmds reservations now include two hosts with the hostname.

The hostname is now returned together with the hosts.

The hostname returned via host_cmds is parsed.