WebUI - notify if a connection to the EMS-ESP drops and refresh on connect

[proddy]

A few cases

1. When clicking Restart from the System tab, there is no response back to the user's browser when EMS-ESP reconnects. This is because the browser session is killed.
2. When uploading a firmware you're never sure if it's done and have to manually shift-R to reload the page and purge the cache

I plan to implement a WebSocket timer that polls the connection and reports if it can't be reached and keeps retrying. On a successful re-connect, a refresh is forced.

[proddy]

Refresh on upload has been implemented in 3.4

[proddy]

I like how the Unifi products do this: