Elm: Use 'canvas' API and structure rather than 'output' API and

Elm: Use 'canvas' API and structure rather than 'output' API and
structure.

'canvas' and 'output' are same. So we need to deprecate one of them
later(may be evas 2.0 or so.) After I discuss this with raster, I've
got to use 'canvas' not 'output'. So I fixed elementary codes.

git-svn-id: https://svn.enlightenment.org/svn/e/trunk/elementary@60268 7cbeb6ba-43b4-40fd-8cce-4c39aea84d33