Fixed EXT-6550(major) - Edit Outfit: Fix alignment of in-line edit button and put proper icon on it

Replaced LLPanelInventoryListItem with LLPanelInventoryListItem. This class is capable of showing widgets on left and right sides of panel.
Implemented LLPanelClothingListItem and LLPanelBodyPartListItem - makes use of new LLPanelInventoryListItem and is able to show buttons specified in tickets. Buttons are
shown on mouse_enter event and hidden on mouse_leave event. Buttons are - delete, move up, move down, lock, edit. It's item's user responsibility
to control buttons visibility.
Made LLInventoryItemsList::addNewItem virtual to allow inheritors create specific(non-default) items.

Reviewed by Mike Antipov - https://codereview.productengine.com/secondlife/r/325/

--HG--
branch : product-engine