[Postfix] Allow to set and override a relayhost per mailbox

[Web] Replace recycle icon with trash (this one made me a bit sad)
[Web] Various small fixes
[Web] Allow or disallow a domain admin to change relayhost settings (default is off, as previous default)

data/web/css/site/edit.css

@@ -40,4 +40,8 @@
 .input-group-addon-xmpp {
   background-color: #fff;
   border: 0px solid #fff;
+}
+#sender_acl_disabled {
+  display:none;
+  margin-top:10px;
 }