More dev-friendly UI

In our previous [experiment](https://github.com/cayleygraph/cayley-web) for the UI we added a cool dev-oriented feature: the "Write" and "Dump" views were showing how you can make the same request as the UI on your own.

For example, for "Read" we showed something like this:
```
GET /api/v2/read?format=nquads
```
It was written in a tiny grey font, so it wasn't too distracting, but gave a clue how you can achieve the same from other systems. I think this was a great way to emphasize that the focus of the project is on the application developers.

For the new UI, I think it doesn't make a lot of sense to add this grey text. Instead, we can add some kind of button that brings up this tip. In this case we will have more space for information and can add a `curl` command that does the same request as well.