progit: update translation status, document rule for sorting them (#2141)

## Changes

 * Update the sorting of translation of progit book
 * State the rule for classifying levels of translations

## Context

Some translators (for Turkish) indicated that their version was
complete.

Author: dscho

layouts/partials/translations.html

@@ -1,3 +1,8 @@
+<!-- the rule for classifying translations is as follows:
+- full translation: all chapters are translated
+- partial translation: at least the first three chapters are translated, but not all
+- translation started: at least the first chapter is translated, but not all of the first three chapters are translated
+-->
 <p>
 This book is available in
   <a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "en") }}">English</a>.
@@ -17,7 +22,9 @@
     <tr><td><a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "nl") }}">Nederlands</a>,</td></tr>
     <tr><td><a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "ru") }}">Русский</a>,</td></tr>
     <tr><td><a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "sl") }}">Slovenščina</a>,</td></tr>
+    <tr><td><a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "sr") }}">Српски</a>,</td></tr>
     <tr><td><a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "tl") }}">Tagalog</a>,</td></tr>
+    <tr><td><a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "tr") }}">Türkçe</a>.</td></tr>
     <tr><td><a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "uk") }}">Українська</a>,</td></tr>
     <tr><td><a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "zh") }}">简体中文</a>,</td></tr>
   </table>
@@ -28,7 +35,8 @@
     <tr><td><a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "cs") }}">Čeština</a>,</td></tr>
     <tr><td><a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "mk") }}">Македонски</a>,</td></tr>
     <tr><td><a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "pl") }}">Polski</a>,</td></tr>
-    <tr><td><a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "sr") }}">Српски</a>,</td></tr>
+    <tr><td><a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "pt-br") }}">Português (Brasil)</a>,</td></tr>
+    <tr><td><a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "sv") }}">Svenska</a>,</td></tr>
     <tr><td><a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "uz") }}">Ўзбекча</a>,</td></tr>
     <tr><td><a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "zh-tw") }}">繁體中文</a>,</td></tr>
   </table>
@@ -40,10 +48,7 @@
     <tr><td><a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "id") }}">Indonesian</a>,</td></tr>
     <tr><td><a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "it") }}">Italiano</a>,</td></tr>
     <tr><td><a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "ms") }}">Bahasa Melayu</a>,</td></tr>
-    <tr><td><a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "pt-br") }}">Português (Brasil)</a>,</td></tr>
-    <tr><td><a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "pt-pt") }}">Português (Portugal)</a>,</td></tr>
-    <tr><td><a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "sv") }}">Svenska</a>,</td></tr>
-    <tr><td><a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "tr") }}">Türkçe</a>.</td></tr>
+    <tr><td><a href="{{ partial "translated-chapter.html" (dict "ctx" . "lang" "pt-pt") }}">Português (Portugal)</a>.</td></tr>
   </table>
 </p>
 <hr class="sidebar"/>