Change Web UI to use WebSocket for RPC

[rojer]

Mongoose OS supports RPC over WebSocket.
We should open a channel and keep it open to make RPC more efficient. This will also allow regular updates of power readings and other status without sending HTTP request each time.

[rojer]

challenges:

• ensure connection is re-established as necessary (e.g. when device reboots)
• when applying new state updates, do not stomp over pending changes to fields made by the user.

[rojer]

https://github.com/mongoose-os-libs/wifi-setup-web-ui can be used for inspiration

[shellyrgbw]

Mongoose OS supports RPC over WebSocket.

We should open a channel and keep it open to make RPC more efficient. This will also allow regular updates of power readings and other status without sending HTTP request each time.

[shellyrgbw]

https://github.com/mongoose-os-libs/wifi-setup-web-ui can be used for inspiration

[juancitomadrid]

I can work in UI.
Let me know needs.

[rojer]

good job @ZeevoX thank you very much!
UX is much better now

[andyblac]

@rojer any chance of beta release ?

[rojer]

i don't intend to cut 2.8 just for this, so we won't call it a beta, but it makes sense to cut a build that can be tested.
i think we should just have latest build always available

[rojer]

i filed an issue for this - #379

meanwhile, i've manually cut a one-off - http://rojer.me/files/shelly/2.7.0-latest/