man,html: say 'systemd 198' in the header

This should help readers of the man or HTML pages know if the documentation
is out of date. An alternative to use a date generated from 'git log' was
considered, but since we try to keep user visible documentation up to date,
showing the project version should be enough.

src/python-systemd/docs/layout.html

@@ -6,7 +6,7 @@
   <a href="index.html">Python </a>·
   <a href="../libudev/index.html">libudev </a>·
   <a href="../libudev/index.html">gudev </a>
-  <span style="float:right">systemd v. {{release}}</span>
+  <span style="float:right">systemd {{release}}</span>
   <hr />
 {% endblock %}