wheelhost: Publish wheels built by Jenkins

The point of the "wheel host" is to serve as a repository of Python
packages (wheels) built by Jenkins for consumption by `pip` et al. For
applications and libraries that do not provide all of their dependencies
as binary packages, this makes a convenient way to install them without
requiring all of the build tools and dependencies on the destination
machine.

The idea here is that a Jenkins job runs `pip wheel` for a distribution
package name or `requirements.txt` file and then uploads the resulting
wheel files using `rsync`. Apache is configured to serve the upload
directory with an index compatible with `pip`'s `--find-links`.

roles/wheelhost/files/wheels.httpd.conf

@@ -0,0 +1,7 @@
+Alias /wheels /var/lib/wheels
+
+<Directory /var/lib/wheels>
+    Require all granted
+    Options +Indexes
+    IndexOptions -FancyIndexing -HTMLTable
+</Directory>