Add a NOT_CONTROLABLE example

[frandominguezl]

Hello! I'm part of WePositive and we needed an example of a non-controllable device for an upcoming partner. We thought it might be useful to include it in the official docs as well.

I have two questions, regarding assets:

1. I have placed the UML diagram under website/static/img/no-control-sequence-diagram.png, but I feel you handle them in a different way. Could you please indicate how to proceed?
2. Normally, the examples have a custom top banner. In this case I couldn't find any references on how to create one so, feel free to either accept this without a custom top banner or create one yourselves for this particular example.

Thanks a lot for the review!

[jorritn]

It's a bit strange that the measurement is a positive value and the forecast negative. I suggest to remove the minus signs.

[jorritn]

Thanks a lot! Nice contribution.

1. The way you added the sequence diagrams is exactly how we are doing it too. So, that's fine.
2. The banner was created by someone else. I don't have the sources either. I'll ask if he can create one for this page too. But it's not a blocker to merge.

[frandominguezl]

@jorritn Thanks for the review and for the answers! I've just pushed a commit that fixes your comments.