Add possibility to disable Server Sent Events in Axon Server UI

[ViliusS]

Newest Axon Server UI sends Server Sent Events (EventStreams) every few seconds from http://axonuiurl/v2/clusterupdates to the browser. Under normal circumstances this is fine, however this doesn't work when UI is behind cloud based load balancer. Most cloud providers do not support Server Sent Events so the EventStream connection timeouts. In result, for example on Google Cloud, Axon Server UI produces this error message every 30 seconds (default timeout of Google Load balancer):

No connection to Axon Server

For some cloud providers you can increase timeout to larger values making the error message appear less often, but this is just a workaround.

It would be great if Axon Server would have an option to disable these UI checks.