Fix to import into Calibre and allow guide section

I was having issues with the title, author and cover page not being recognised when importing epub files generated with DotNetEpub into Calibre.

After going through a few articles determining the best ways to ensure a cover page is displayed ( I added the guide section as a part of this, and the OPF name space to the meta tags ), I eventually ran Calibre in debug mode ("calibre-debug -d").  This highlighted that the version used in the container.xml was incorrect.  It should always be version 1.0.

This series of commits will allow the correct version for the content.xml, specification of references in the guide section, and successful importing into Calibre.