cleanup content type icons

view/theme/dispy/style.css

@@ -814,7 +814,7 @@ section { margin: 10px 11% 0px 11%; font-size: 0.8em; padding-right: 230px;}
 
 .attachtype {
 	display: block; width: 20px; height: 23px;
-	background-image: url('../../../images/content-types.gif');
+	background-image: url('../../../images/content-types.png');
 }
 
 .type-video { background-position: 0px; 0px; }

view/theme/duepuntozero/style.css

@@ -2434,7 +2434,7 @@ a.mail-list-link {
 .attachtype {
 	display: block; width: 20px; height: 23px;
 	float: left;
-	background-image: url('../../../images/content-types.gif');
+	background-image: url('../../../images/content-types.png');
 }
 
 .body-attach {

view/theme/loozah/style.css

@@ -2450,7 +2450,7 @@ a.mail-list-link {
 .attachtype {
 	display: block; width: 20px; height: 23px;
 	float: left;
-	background-image: url('../../../images/content-types.gif');
+	background-image: url('../../../images/content-types.png');
 }
 
 .body-attach {