EXT-7722 Fixed "Add to COF" and "Remove from COF" outfit context menu items to...

EXT-7722 Fixed "Add to COF" and "Remove from COF" outfit context menu items to be enabled when appropriate and work properly.

Work on "Take Off - Remove from Current Outfit" and "Wear - Add to Current Outfit" menu options:
- The menu items of the outfit context menu and the My Outfits gear menu are now disabled
  when inappropriate instead of being hidden.
- The menu items get enabled/disabled depending on whether you can wear (take off) anything from the selected outfit.
  (was: depending on whether you're wearing the outfit)
- Changed the way the options work: they now only operate on clothes and attachments.
  "Add to COF" now only adds those body parts that are missing in COF;
  "Remove from COF" doesn't touch body parts at all.

  Without this change both "Add" and "Remove" options would be available simultaneously, because
  any valid outfit contains body parts. I think that would be confusing.
  And you don't expect you body parts to be replaced when doing "Add to COF'. (that's addition, not replacement)

Reviewed by Mike Antipov at https://codereview.productengine.com/secondlife/r/585/

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branch : product-engine