* Logically organize the Whonix-related pages
* Move the VPN page to /configuration/
* VPNs are used for more than just privacy, and many VPN setups and
services either can't or don't claim to provide privacy.
* Remove `/privacy/` from URLs
* These directory names are just for organizing the source pages,
*unless* an actual page resides there. Since there is no
/doc/privacy/ page, it's unnecessary and misleading to have this in
the URLs. It also breaks uniformity, since none of the other pages
have their informal group name in their URL (again, unless there's
a page with that name).
This commit creates a single, central page (/doc/usb/) for all
USB-related information by combining stick-mounting.md with the
manual USB qube (formerly known as "USBVM") creation procedure
from security-guidelines.md. It rewrites the content from both of
those and adds the content requested in QubesOS/qubes-issues#1690.
It also redirects /doc/usbvm/ away from the ancient page on PVUSB.
