Add none to appearance values

Mozilla and WebKit use none as a reset value

Author: nschonni

src/css/Properties.js

@@ -42,7 +42,7 @@ var Properties = {
     "-o-animation-name"                : { multi: "none | <ident>", comma: true },
     "-o-animation-play-state"          : { multi: "running | paused", comma: true },        
 
-    "appearance"                    : "icon | window | desktop | workspace | document | tooltip | dialog | button | push-button | hyperlink | radio-button | checkbox | menu-item | tab | menu | menubar | pull-down-menu | pop-up-menu | list-menu | radio-group | checkbox-group | outline-tree | range | field | combo-box | signature | password | normal | inherit",
+    "appearance"                    : "icon | window | desktop | workspace | document | tooltip | dialog | button | push-button | hyperlink | radio-button | checkbox | menu-item | tab | menu | menubar | pull-down-menu | pop-up-menu | list-menu | radio-group | checkbox-group | outline-tree | range | field | combo-box | signature | password | normal | none | inherit",
     "azimuth"                       : function (expression) {
         var simple      = "<angle> | leftwards | rightwards | inherit",
             direction   = "left-side | far-left | left | center-left | center | center-right | right | far-right | right-side",