issue #1175 redesign plugin manager

* design based on Samuel's mockup + Hannah's adaptations
* on each plugin actions shown as buttons in a single column (better compatibility with verbose languages such as German)
* description always shown (no more need of the "show details" action)
* filter based on plugin title/description (javascript, no page reload)
* hide inactive plugins if they are 8 or more
* plugins no longer shown in the admin left menu, they instead get a "settings" action if relevant. Compatible with the old trigger get_admin_plugin_menu_links but new method is to simply add a "Has Setting : true" in the main.inc.php header

admin/themes/default/template/admin.tpl

@@ -91,14 +91,6 @@ jQuery(document).ready(function() {
       <ul>
         <li><a href="{$U_PLUGINS}"><i class="icon-equalizer"></i>{'Manage'|@translate}</a></li>
       </ul>
-{if !empty($plugin_menu_items)}
-      <div id="pluginsMenuSeparator"></div>
-      <ul class="scroll">
-  {foreach from=$plugin_menu_items item=menu_item}
-        <li><a href="{$menu_item.URL}">{$menu_item.NAME}</a></li>
-  {/foreach}
-      </ul>
-{/if}
 		</dd>
   </dl>
   <dl>