Save attachment data for attachment model/skeleton model combinations, let
scripts use those saved parameters so that you can tweak the location of
(for example) the gun and have it saved appropriately.
Merge branch 'master' of https://github.com/highfidelity/hifi
Merge pull request #2822 from ey6es/master

Save attachment data for skeleton/attachment combinations so that they persist even when the attachment isn't present, and users can tweak script-attached models.