EXT-7777 WIP Implemented loading indicator for "Save" and "Save As" actions in...

EXT-7777 WIP Implemented loading indicator for "Save" and "Save As" actions in "My Outfits" & "Edit Outfit" Panels.
EXT-7929 FIXED Updated functionality of attaching object: loading indicator gets hidden when attaching is completed.

- Fixed crash when accessing singleton on application exit.

- Updated functionality of attaching object: loading indicator was not hidden.
 * Reason: link to attachment was created without next appearance updating.
 * Fix: passed "true" into LLAppearanceMgr::addCOFItemLink to call LLAppearanceMgr::updateAppearanceFromCOF when attachments is completed. (Like for clothing).

Reviewed by Vadim Savchuk at https://codereview.productengine.com/secondlife/r/611/

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branch : product-engine