Allow HTML in tooltips

[mar10]

See here: https://groups.google.com/forum/#!topic/fancytree/-YBJHqLFeoQ

If system <span title="TEXT">can deal with special chars (by escaping it), we don't have to do the escaping when nodes are initialized.
This would allow external tooltip plugins to make use of HTML formatted content

See also #197: we still have to escape ' as &

See also http://stackoverflow.com/a/15734408/19166 and http://bugs.jqueryui.com/ticket/9019 why this might be no good idea.

[mar10]

Note: HTML in the title attribute is invalid!

Still we do not escape the tooltip text before writing it to the <span title="TEXT"> attribute, so it is up to the sender to make sure this is escaped, if he wants the markup to be valid HTML.

Note that the browsers default popups do not support HTML markup anyways: tags will be escaped.
jQuery UI Tooltip also stopped supporting it starting with release 1.10. See here for a workaround:

[ {title: "node 1.1", "tooltip": "A <b>bold</b> tooltip's text"}, 
  ... ]

$("#tree").tooltip({
    content: function () {
        return $(this).attr("title");
    }
});

A compliant way to implement HTML formatted tooltips would be to pass the content in a custom field and let the tooltip use it:

[ {title: "node 1.1", "hoverInfo": "A <b>bold</b> tooltip's text"}, 
  ... ]

$("#tree").tooltip({
    items: "span.fancytree-title",
    content: function () {
        var node = $.ui.fancytree.getNode(this);
        return node.data.hoverInfo;
    }
});