completed EXT-6721 (Enable UI for user modification of wearable order)

- added functionality to change order of wearables
- added ad-hoc up and down buttons on a button bar ("up" means closer to the body) - https://jira.secondlife.com/secure/attachment/38464/screenshot-1.jpg
- added displaying wearables as sorted by order on the Edit Outfit panel (top list)

Reviewed by Neal Orman at https://codereview.productengine.com/secondlife/r/280/

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branch : product-engine