Set all signatures use gray background by default.

Previoulsy they were white on white, which was a horrible default.

template/resources/sass/_class_overview.scss

@@ -44,7 +44,6 @@
   .signature {
     font-weight: bold;
     text-transform: uppercase;
-    color: white;
     font-size: 0.7em;
     @include border-radius(2px);
     margin-left: 5px;

template/resources/sass/_hover_menu.scss

@@ -55,8 +55,6 @@
       font-weight: bold;
       padding: 0 0.5em;
       @include border-radius(2px);
-      color: white;
-      background: #aaa;
       @include signature-colors; } } }
 
 .hover-menu a {

template/resources/sass/_mixins.scss

@@ -146,10 +146,12 @@
 
 // Shared colors for member signatures in toolbar menu and class api body
 @mixin signature-colors {
+  // the default colors
+  color: white;
+  background-color: #aaa;
+  // specific colors
   &.deprecated {
     background-color: #aa0000; }
-  &.protected, &.template, &.readonly, &.abstract {
-    background-color: #aaa; }
   &.static {
     background-color: $docs-text-color; }
   &.required {