Add explanation section

[ricklambrechts]

Basic working implementation of how we could implement an explanation section for a specific state.

Would like to receive feedback!

Yivi popup issuing flow in dutch with the changes in our application.

After scanning the QR code with the Yivi app, the explanation is gone. I think the explanation is also not needed because of the message that is visible. But it is possible to add another explanation based on the state in the language files.

Currently the height is fixed. We need to update that to support this additional section.

yivi-frontend-packages/yivi-css/src/components/yivi-form.scss

Lines 86 to 88 in da76c44

	// Acts as min-height, but IE11 needs a fixed
	// parent height for the vertical centering.
	height: $qr-code-size + 224px;

[MikeClickr]

Well done @ricklambrechts ! I oppose to use the following text for mobil use:
Gebruik uw Yivi-app om uw gegevens door te geven.

[ricklambrechts]

When you are on mobile you see state 3b.

[bobhageman]

Very nice improvement! One thing: I would like to keep the translation files as plain as possible. Thereby I suggest to move the explanation: function(... logic out of nl.js and en.js.

And it might also be fine to enable the explanation by default (showExplanation=true) but that's something we will discuss first.

[bobhageman]

@ricklambrechts, we've decided the explanation should not be enabled by default to maximize backwards compatibility. Therefore you can leave that setting as is;)