Jetty configuration wiki page and configuration to help mitigate clickjacking

[Scott Koranda]

> > If the team is amenable I am happy to make the edits directly, or I could send
> > proposed edits along if the team would prefer to make edits directly.
> 
> There's native support in 3.4 for some of that using a filter but it's fine with me.
> 

I have made the edit to the wiki.

Please let me know if you would like me to change anything or revert.

Thanks,

Scott K