Fixed EXT-7163(normal) - Create dummy inventory item panel (an item panel for...

Fixed EXT-7163(normal) - Create dummy inventory item panel (an item panel for unworn wearable types)
Added new wearable list item - LLPanelDummyClothingListItem for not worn wearable types, it displays grayed wearable type icon, grayed
title '<clothing type> not worn' and 'add' button.
Modified base class to be more flexible.
Moved init() to protected section.
Modified COF panel to use dummy item.

Reviewed by Mike Antipov - https://codereview.productengine.com/secondlife/r/335/

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branch : product-engine