Screen is only in the center movable

[mstich0]

Currently when one is zooming out in the editing page the energy system it is only possible to move around (with left mouse click and drag) when klicking inside the original area that was visible when entering this page. When clicking outside the purple marked area it is not possible to move around (and thats bad).

[Bachibouzouk]

This goes hand in hand with #269

[Bachibouzouk]

closed by #325