Web page auto-reload upon server upgrading

[Toparvion]

Is your feature request related to a problem? Please describe.
Currently there is a chance to break the web client if it keeps working while the server is being upgraded.

Describe the solution you'd like
It seems feasible to trigger client reloading in order to make it aligned with the server API and behavior as soon as possible.

Describe alternatives you've considered
We could also support strict backward-compatibility between the web client and the server. While generally a good practice, it looks too expensive in this situation because web clients are usually not separated from the corresponding servers.

Additional context
In order to keep user experience smooth, it is desirable to provide a non-modal dialog (e.g. a pop-up) informing about forthcoming upgrading and suggesting to reload the client right now. This can be done the way instant messaging web clients behave.