Improve Docbook and reference guide titles and breadcumb/rendering

[fyodor]

@dmiller-nmap and I were just discussing some pages on the new site like https://npcap.com/guide/index.html which currently repeats "Npcap: Nmap Project's packet sniffing library for Windows" 4 times near the top. Two in the purple bar and then once centered and bolded below that, and then in large bold text below that. And then it comes to the table of contents. Other Docbook pages we host have similar issues, though usually not quite that bad (and for some these breadcrumbs are beneficial). So were were thinking of doing something like:

• Rename the Npcap guide something like "Npcap Reference Guide" rather than "Npcap: Nmap Project's packet sniffing library for Windows" so references to the title aren't so verbose.
• Dan is working on some cool breadcrumbs navigation for libpcap API docs which could be expanded to our other Docbook-generated pages: https://npcap.com/guide/wpcap/pcap_strerror.html.
• Dan was talking about removing the document name from the purple titlebar and possibly document title, especially if we have new breadcrumb navigation providing the context.

These approaches aren't set in stone. Dan may come up with different/better ways to handle it. But we wanted to add this ticket so we don't forget about it.