build: Fix indexing so it works on HTML and PDF.

- Remove all genindex.rst files, these are generated and should not
  exist in our source.
- Fix the HTML templates so the local specialisation works.
- Add a index link to the sidebar for HTML.

Note, there is no TOC entry for the index in the PDF output and I
cannot figure out how to add one.

Closes #3503

common/conf.py

@@ -34,7 +34,7 @@ extensions = [
 ]
 
 # Add any paths that contain templates here, relative to this directory.
-templates_path = ['build/_templates']
+#templates_path = ['build/_templates']
 
 # The suffix of source filenames.
 source_suffix = '.rst'
@@ -202,7 +202,9 @@ latex_elements = {
     'preamble':     r'''
 \newcommand{\rtemscopyright}{%s}
 \usepackage{rtemsstyle}
-''' % (copyright)
+''' % (copyright),
+    'printindex': r'\footnotesize\raggedright\printindex',
+    'parsedliteralwraps': True,
 }