Functional Safety Editor: Double-click diagram to add a comment

[MichaelBalzer]

Comments can be added to the diagram in the Functional Safety Editor, but only when dragged from the palette. It's second nature in LabVIEW to simply double-click a blank area of the block diagram and begin typing to add a comment, so the lack of this feature in the FSE is really jarring.

This idea is to enable double-clicking an empty area of the diagram to automatically insert a comment, without the need to drag it in from the palette.