Changed "Add to view..." to the same label as the menu item: "Add variables to view..."
OPAL-1793: Explicitely copying categories when deriving a variable to add to a view
Work on OPAL-1790: Derive from overwrite categories
Fix OPAL-1790: Derive from overwrite categories
OPAL-1793: Fixed DerivedVariableGenerator to correctly copy categories.
Still working on OPAL-1790: Derive from overwrite categories
Merge pull request #168 from emorency/master

OPAL-1793: Explicetily copying variables categories when adding to view