* Finish compatibility work.

* Fix <pluginFlowable> tag to the following form::

  <pluginFlowable module="..." function="...">
    <param name="color" type="Color">#FF0000</param>
    ...
  </pluginFlowable>

* Add TOC

* Add chart legends

* Add symbols

* Implement form fields: push button, text field, select field

  See reportlab.pdfbase.pdfform
