[Xsltforms-support] Add link to wikibook on xsltforms welcome pages

[Kostis A. <ank...@gm...>]

Hi Alain,

In order to help xform-authors and to facilitate contributtors to
project's documentation,
it would be good if you added the link to the wiki-books:
  http://en.wikibooks.org/wiki/XSLTForms
on pages:
a) http://www.agencexml.com/xsltforms (since it is the first page on searches)
b) https://sourceforge.net/projects/xsltforms/ (somewhere on project details)

Thank you,
  Kostis