Merge appendChildToContainer into ContainerNode

We don't need the templates in ContainerNodeAlgorithms now,
lets start merging them into ContainerNode.

Review URL: https://codereview.chromium.org/329703002

git-svn-id: svn://svn.chromium.org/blink/trunk@175968 bbb929c8-8fbe-4397-9dbb-9b2b20218538