Changed standard_html_header, standard_html_footer, and standard_error_message to use new DTML syntax.

<dtml-var zope_quick_start>

instead of the old, inaccurate and hard-to-edit "Welcome to Zope" page

Added __len__ method of sequence_variables class for processing of len inside cDocumentTemplate len function when they're pushed on the stack.

Changed manage_access to work properly, and converted RoleManager's manage_access to use DTMLFile instead of HTMLFile.

dependency.