Realize the data bridge

[Sing-Li]

Currently in the "Demo Mode", there are three pieces of data displayed:

• total users
• online users
• messages sent

And these numbers are magic number constants.

It would be a good incremental step to realize these numbers by:

1. accepting the URL of a Rocket.Chat server to be specified
2. accepting entry of the credentials for REST API against the Rocket.Chat server in (1)
3. make the appropriate REST API calls and obtain the actual up to date counts from the server
4. display them in the "Demo Mode"
5. keep this a regular update, on a "user specified interval" - default to 30 minutes