docs: add pages to support Go module package resolution

docs: add pages to support Go module package resolution

Currently the libvirt Go modules are accessed by applications using
their github repository URLs. This is undesirable as we don't want
applications to have a direct dependancy on a specific source repo
location. We want to enable applications to use the Go packages via
the libvirt.org namespace.

When you do "go get libvirt.org/libvirt-go", the Go client will do an
HTTPS request to that URL, and parse the HTML content to look for a
<meta> tag which tells it where to the find the GIT repository.

   https://golang.org/cmd/go/#hdr-Remote_import_paths

This adds two pages to support this Go module resolution. They are
not linked from anywhere as we don't expect users to actually look
at them. If someone does happen upon them, there's some boilerplate
text to send them off to godoc.org for API documentation.

Since the pages we're adding have a .html extension, we will also
use a small apache config tweak on the server

    RewriteEngine on
    RewriteRule ^/libvirt-go$ /libvirt-go.html [L]
    RewriteRule ^/libvirt-go-xml$ /libvirt-go-xml.html [L]

Reviewed-by: Jiri Denemark <jdenemar@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>