Bug fix

Check if HG object is being deleted
Bug fix

To address a bug in Matlab copyobj
Bug fix

Must return output arguments even if nothing is visible
Bug fix

Return value even if nothing is visible
Bug fix

No layout if nothing is visible
Added new property: ElementsFlowing

Turning on this property makes elements to reflow when GridSize is
changed
Bug fix

To reduce unnecessary layout_panel calls
Added new property: ElementsFlowing
Bug fix

To account for an Enable property without "inactive" option
Bug fixes

as uiscrollpanel went through its first real usage
Split uizoomctrl -> uizoomctrl + zoompanctrl

Pulled out UI-free zoom/pan control functions as a separate class
Minor documentation update