0.76.0

• Added Application._executeStartupFiles() method (#354).
• Added RemoveChannels image node.
• Added a PointConstraint node (#482).
• Fixed framing error when entering a Box.
• Image viewer now displays channels in grey scale.
• Added Widget.widgetAt() method.
• Added ability to hide tabs in layouts.
• Fixed bug converting coshader array from fixed to variable length.
• Added Serialiser::postScript() method.