Description

Fixes and improvements related to the new feature to lock the elements on the worksheet:

don't allow to move the element with the mouse or with the cursor keys if it's locked, react on all other events
don't add the lock action to the context menu for elements which cannot be freely moved on the worksheet (like axis and curves/plots)
hide the option "Lock" in the dock widget for the text label if the label is child of an axis, the label cannot be freely moved in this case
added "Locked" property in the dock widgets for legend, custom point, image, reference line and reference range

Conformity