revise coupling between experimental data and instrument model

This is related to the problems

• of scaling coordinate axis #614 (closed),
• of notification between widgets #503.

added META label

mentioned in issue #614 (closed)

marked this issue as related to #565 (closed)

marked this issue as related to #357 (closed)

marked this issue as related to #331 (closed)

marked this issue as related to #301 (closed)

marked this issue as related to #190 (closed)

changed the description

mentioned in issue #666 (closed)

Absorbed into #666 (closed).

closed