Extend and update WebDav how to article

[rschwietzke]

Challenge

We receive many search hits via Google for https://docs.xceptance.com/xlt/load-testing/test-suites/40-webdav-test-suite/ but our page is rather ... reduced.

Task

Update the test suite to latest XLT, make sure it also has other dependencies updates, verify the functionality, ensure that the README is updated and formatted correctly. Ensure that the README is a good starting point.

Take the freedom to copy most of the readme stuff to the documentation so that we don't just hit the reader with links but have some interesting text in context. The links to the GITHUB projects good, but not just what we should put out there.

The doc should be interesting reading here, maybe one can also drop a hint on how we integrated that or made WebDav work with XLT.