docs/pwg/: First try to resurrect the PWG. I'm halfway integrating the mimetypes and will from there on work on both ...

Original commit message from CVS:
2004-01-26  Ronald Bultje  <rbultje@ronald.bitfreak.net>

* docs/pwg/advanced_types.xml:
* docs/pwg/intro_basics.xml:
* docs/pwg/intro_preface.xml:
* docs/pwg/pwg.xml:
* docs/pwg/titlepage.xml:
First try to resurrect the PWG. I'm halfway integrating the mimetypes
in here (docs/random/mimetypes), and will from there on work on both
updating outdated parts and adding missing parts.
That doesn't mean I'll fix it completely, but I'll try at least. ;).