Add elevator questions

[wielandb]

This PR adds some questions that relate to the recent "Evelator dimensions" proposal.

These questions are:

• What shape does this elevator have?
• What's the diameter of this elevator?
• How tall is the cabin of this elevator?
• How wide is the door of this elevator?
• How tall is the door of this elevator?

It modifies the questions

• How wide is this elevator?
• How deep is this elevator?
  to only be asked if the elevator has a rectangular shape

It does not ask for any max*:physical=*values as this is currently not possible with this app.

Currently missing:

• Example images

[wielandb]

The JSON validation fails.

I don't really understand what's wrong about

            "max": 4,
            "unit": "@unitCentimeter"
         },
         "constructor": {
            "diameter": ["CONCAT", "$input", "m"]
         }
      },

[Robbendebiene]

Move all new elevator questions right below the elevator width/length questions.