Introduction of "ConvertTo" family of plugins. This establishes a new inheritance hierarchy.
BasPlug -> ConvertToBasPlug -> HTMLPlug/TEXTPlug -> ConvertToPlug -> PDFPlug/WordPlug/Future application plugins
BasPlug -> ConvertToBasPlug -> HTMLPlug/TEXTPlug -> ConvertToPlug
-> PDFPlug/WordPlug/Future application plugins