completed EXT-6719 Utilize the "description" field of outfit wearable links to store order information

- COF items get checked for correct ordering when COF is loaded (LLAppearanceMgr::updateAppearanceFromCOF..., LLAppearanceMgr::updateClothingOrderingInfo() ), and also when COF is saved to a new outfit, base outfit.
- wearables are arranged in LLAgentWearables in a proper order

* updateClothingOrderingInfo() [struggling with naming] does integrity checking and updates "invalid" items (items with wrong, gapped descriptions)
* moved LLAgentWearables::makeNewOutfitLinks(...) and LLShowCreatedOutfit  to a more natural place (llappearancemgr.cpp), because they use LLAppearanceMgr's methods a lot
* changed link_inventory_item(...), added the "new_description" parameter

Reviewed by Neal Orman at https://codereview.productengine.com/secondlife/r/268/

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branch : product-engine