ADDED: Initial copy of SVG tree
Changed SVG label class to "tree-label" to avoid bootstrap influence.
Using getComputedStyle seems not portable.  Now using jquery to compute
the text style properties, but still getting 0 :-(  hard-coded to make
some sense.
Removed dominant-baseline:text-after-edge !important.  Looks ugly.
Cleanup
Remove console.log
scrollToBottom must iterate over runners.
FIXED: Add a short delay before scrolling the runner to give ajax script
the time to do their work.  A timeout is not elegant, but I have not found
a better solution yet.  See lib/render/svgtree.pl, which suffers from the
fact that tree.draw() called before this stuff is part of the DOM tree.
MODIFIED: Do not use jQuery .html() to append answers, but innerHTML
followed by executing the embedded scripts.  This ensures the elements
are already part of the DOM and can inspect their parents.
Simplify SVG tree CSS
FIXED: adding HTML nodes to the SVG tree
Added a noleaf class to non-leaf nodes.
Use HTML rendering for leaf nodes.
Use the new SVG renderer for the DCG examples.
Provide $.ajaxScript while executing ajax downloaded scripts.
Document and avoid the need for using an id attribute in generated
HTML rendering.
ADDED: Support filtering to render structures as a tree.