Many small refinements to front/backend UI

Changes:
 - Added a friendlyTime helper for nicer timestamps
 - Added validation to most action methods
 - Added error flash to several template files
 - Now making use to c.RenderError() to handle action errors
 - Removed message list slideUp() effect, takes too long
 - Fixed a problem with my vim indentation configuration, so CSS and
   HTML should be indented more consistently.

app/views/Mailbox/List.html

@@ -1,9 +1,9 @@
 {{$name := .name}}
 {{range .messages}}
 <div class="box listEntry" id="{{.Id}}">
-	<div class="subject">{{/*<a href="/mailbox/show/{{$name}}/{{.Id}}">*/}}{{.Subject}}</div>
+	<div class="subject">{{.Subject}}</div>
 	<div class="from">{{.From}}</div>
-	<div class="date">{{.Date}}</div>
+	<div class="date">{{friendlyTime .Date}}</div>
 </div>
 {{else}}
 <div class="box">