Revision 1694754

Code cleanup:  this should eventually go into a JIRA issue...

Small changes to allow ComponentNode and ImageNode to actually work inside
a TextPane.  Not sure of the reasons, but it was very difficult to get this
to work without turning both into subclasses of Block instead of Node.

Now, at least, one can insert either straight into a Document and then into
a TextPane and they will work.  Update the HyperlinkButtonTest program to
illustrate this.