[ADD] legal: update contracts for new maintenance

- Update Enterprise & Partnership agreement (EN, FR)
- Update legal page index: hide outdated agreements, replace
  with a link to an archive of the old PDFs.
- Add icons for missing files, to make index table layout more consistent
- Add `text-justify` on HTML versions of contracts, for consistency with
  the PDF versions.
- Fix compatibility of PDF generation with recent sphinx versions
  (\sphinxmaketitle instead of \maketitle)
- Re-add NL PDF building, still needs to be updated like all others

Backport of 5b80ed551c from 13.0

_static/latex/odoo.sty

@@ -95,6 +95,20 @@
 }
 
 
+% For sphinx 1.8.3+, the command is \sphinxmaketitle and the
+% layout is slightly different on the titlepage
+\renewcommand{\sphinxmaketitle}{%
+  \noindent\rule{\textwidth}{1pt}\par
+  \begin{flushright}
+    \sphinxlogo
+    \py@HeaderFamily
+    {\hspace{-0.5cm} \huge \@title }\par
+  \end{flushright}
+  \@thanks
+  \setcounter{footnote}{0}
+  \let\thanks\relax\let\maketitle\relax
+}
+
 \newcommand{\makeodootitleold}{%
   \begin{titlepage}
   \titlepagedecoration