renaming "Beautify Fill" to "Beautify Faces"

changing the ot->name only, not the ot->idname
(to avoid breaking scripts)

The tool requires the selection to be fill previously,
the original name was confusing if we consider we have
"Fill" with the "Beauty" option.

Discussed with Bastien Montagne and Brecht van Lommel.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk@60782 954f8c5b-7b00-dc11-b283-0030488c597c