Normalize sidebar in docs

A new version of the alabaster theme changed how the logo is handled.
Correct that and add previous/next links.  This realigns the docs
with Zuul.

Change-Id: Icd19284e4d3c054a8ad4eeed42e1d93ca87f86bd

doc/source/conf.py

@@ -94,7 +94,10 @@ pygments_style = 'sphinx'
 # Theme options are theme-specific and customize the look and feel of a theme
 # further.  For a list of options available for each theme, see the
 # documentation.
-#html_theme_options = {}
+html_theme_options = {
+    'show_related': True,
+    'logo': 'logo.svg',
+}
 
 # Add any paths that contain custom themes here, relative to this directory.
 #html_theme_path = []
@@ -108,7 +111,7 @@ pygments_style = 'sphinx'
 
 # The name of an image file (relative to this directory) to place at the top
 # of the sidebar.
-html_logo = '_static/logo.svg'
+#html_logo = '_static/logo.svg'
 
 # The name of an image file (within the static path) to use as favicon of the
 # docs.  This file should be a Windows icon file (.ico) being 16x16 or 32x32