Add proper error handling to XMLExporter extractSiteXML, create XML directory if it doesnt exist
Added error handling code to investigate topic save failures
Parent pages are now properly created in foswiki when detected
Fix Convertor::saveAttachment when attachment doesnt exist

Previously the non-existent path is passed to Foswiki::Func::saveAttachment,
which errors and exits when the attachment doesn't exist. Convertor doesn't
expect this - it expects a non-0 return result
Attempt to add line breaks to work around foswiki ignoring newlines

Without this, if text in a paragraph was split into different lines,
foswiki will run it together (I have a lot of text like this).

This is a hack, as it introduces unwanted breaks to verbatim blocks
and probably some other breakages