Adding new children does not cause Drag and Drop to stop working

Because child tree nodes were detached Drag-and-Drop would stop working
on child nodes
Use the same path for the cloned content so we do not have to rewrite image links in the HTML
Fetch the images when making a copy of content

so they are in the HTML when someone clicks to edit
fix typo
Merge remote-tracking branch 'origin/phil-add-button-fixes2' into github-refactor-oerpub