Implement a simple form to save custom markdown-enabled content in the

forge's admin area that is displayed instead of the default project list.
Sanitize the URLs that we're using and make a redirect to the listProjects
page when no custom forge page is enabled.

src/IDF/templates/idf/gadmin/base.html

@@ -39,6 +39,7 @@
     {include 'idf/main-menu.html'}
 <div id="header">
 <div id="main-tabs">
+  <a href="{url 'IDF_Views_Admin::forge'}"{block tabforge}{/block}>{trans 'Forge'}</a>
   <a href="{url 'IDF_Views_Admin::projects'}"{block tabprojects}{/block}>{trans 'Projects'}</a>
   <a href="{url 'IDF_Views_Admin::users'}"{block tabusers}{/block}>{trans 'People'}</a>
   {if $usherConfigured}