Wrap each addon settings form in their own form tag

- The single form tag was preventing a given addon settings to be saved if another addon had an empty required field.
- Instead of concatenating the addon form HTML through Hook::callAll, we loop manually through the hooks, appending the HTML to an array.

view/theme/frio/templates/settings/addons.tpl

@@ -2,11 +2,17 @@
 	{{* include the title template for the settings title *}}
 	{{include file="section_title.tpl" title=$title}}
 
+{{foreach $addon_settings_forms as $addon_settings_form}}
+
 	<form action="settings/addon" method="post" autocomplete="off">
-	<input type="hidden" name="form_security_token" value="{{$form_security_token}}">
-
-	{{$settings_addons nofilter}}
-
+		<input type="hidden" name="form_security_token" value="{{$form_security_token}}">
+		{{$addon_settings_form nofilter}}
 	</form>
 
+{{foreachelse}}
+
+	<div class="alert alert-info" role="alert">{{$no_addon_settings_configured}}</div>
+
+{{/foreach}}
+
 </div>