Rework rectangular tree aspect ratio UI & code

Currently in UGENE we have 2 options that change aspect ration of rectangular layout branches: width & height sliders.

The same result can be reached with the only one slider and other tool call this option: expansion.

Not using width/height terminology also allows adding other tree options: like rotation.

The task is to rework tree height/width slider into a single expansion slider.

See attached images for details