Reactivate magnifying glass

As originally implemented for Stellwand, there should be an item "magnifying glass" which allows you to highlight connected signalboxes or signals.
This should work by clicking on a signal or signalbox with this item.

Dev-Note:
No direct usage of OpenGL! Access will be removed with new UMC version.

• Add highlighting for signals

• Add highlighting for complex-signals

• Add highlighting for signalboxes

• Merge into develop

• Merge into release/umc-2.0