Replace references to pkg_add with pkg install
Replace links to pkg_add man page with links to pkg-install
Remove references to manually downloading packages, or specifying an ftp url
Remove link to pointyhat that no longer resolves
Update the svnweb link to point directly to the ports tree
use &base; entity everywhere
Use https where applicable

PR: 193370
Reviewed by: gavin
Approved by: bcr
Sponsored by: ScaleEngine Inc.
CR: D732