brands: hardcode ISSUE_URL and some links on the about-page

A *brand* of searx is a fork which might have its own design and some special
functions which might bee reasonable in a special context.

In this sense, the fork might have its own documentation but not its own issue
tracker.  The *upstream* of a brand is always https://github.com/asciimoo from
where the brand-fork pulls the master branch regularly.  A fork which has its
own issue tracker is a spin-off and out of the scope of the searx project
itself.  The conclusion is:

- hard code ISSUE_URL (in the Makefile)
- always refer to DOCS_URL
- links in the about page refer to the *upstream* (searx project)
  except DOCS_URL
- "fork me on github" ribbons refer to the *upstream*

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

searx/templates/__common__/about.html

@@ -7,7 +7,7 @@
     <ul>
         <li>searx may not offer you as personalised results as Google, but it doesn't generate a profile about you</li>
         <li>searx doesn't care about what you search for, never shares anything with a third party, and it can't be used to compromise you</li>
-        <li>searx is free software, the code is 100% open and you can help to make it better. See more on <a href="{{ brand.GIT_URL }}">github</a></li>
+        <li>searx is free software, the code is 100% open and you can help to make it better. See more on <a href="https://github.com/asciimoo/searx">github</a></li>
     </ul>
     <p>If you do care about privacy, want to be a conscious user, or otherwise believe
     in digital freedom, make searx your default search engine or run it on your own server</p>
@@ -22,15 +22,14 @@ Searx can be added to your browser's search bar; moreover, it can be set as the
 
 <h2>How can I make it my own?</h2>
 
-<p>Searx appreciates your concern regarding logs, so take the <a href="{{ brand.GIT_URL }}">code</a> and run it yourself! <br />Add your Searx to this <a href="{{ brand.SEARX_URL }}">list</a> to help other people reclaim their privacy and make the Internet freer!
+<p>Searx appreciates your concern regarding logs, so take the <a href="https://github.com/asciimoo/searx">code</a> and run it yourself! <br />Add your Searx to this <a href="{{ brand.PUBLIC_INSTANCES }}">list</a> to help other people reclaim their privacy and make the Internet freer!
 <br />The more decentralized the Internet is, the more freedom we have!</p>
 
 
 <h2>More about searx</h2>
 
 <ul>
-    <li><a href="{{ brand.GIT_URL }}">github</a></li>
-    <li><a href="https://www.ohloh.net/p/searx/">ohloh</a></li>
+    <li><a href="https://github.com/asciimoo/searx">github</a></li>
     <li><a href="https://twitter.com/Searx_engine">twitter</a></li>
     <li>IRC: #searx @ freenode (<a href="https://kiwiirc.com/client/irc.freenode.com/searx">webclient</a>)</li>
     <li><a href="https://www.transifex.com/projects/p/searx/">transifex</a></li>
@@ -48,8 +47,8 @@ Searx can be added to your browser's search bar; moreover, it can be set as the
 
 <h3>New engines?</h3>
 <ul>
-    <li>Edit your <a href="{{ brand.GIT_URL }}/blob/master/searx/settings.yml">settings.yml</a></li>
-    <li>Create your custom engine module, check the <a href="{{ brand.GIT_URL }}/blob/master/examples/basic_engine.py">example engine</a></li>
+    <li>Edit your <a href="https://github.com/asciimoo/searx/blob/master/searx/settings.yml">settings.yml</a></li>
+    <li>Create your custom engine module, check the <a href="https://github.com/asciimoo/searx/blob/master/examples/basic_engine.py">example engine</a></li>
 </ul>
 <p>Don't forget to restart searx after config edit!</p>