stylesheets: rename *.css.scss -> *.scss.

Fixes "DEPRECATION WARNING: Extra .css in SCSS file is unnecessary."

app/assets/stylesheets/common/page_header.scss

@@ -0,0 +1,45 @@
+@import "000_vars.css.scss";
+
+#maintoggle {
+  display: none;
+}
+
+header#top {
+  h1 {
+    font-size: 2.5em;
+    margin: 5px 30px 0 30px;
+  }
+
+  menu {
+    margin-top: -2px;
+    background: $menu_color;
+    padding: 6px 20px;
+
+    form {
+      display: inline-block;
+
+      input {
+        width: 9.5em;
+      }
+    }
+
+    li {
+      margin: 0;
+      padding: 0;
+    }
+
+    li a {
+      padding: 6px 10px;
+    }
+  }
+
+  menu.main {
+    margin-top: 0;
+    background: none;
+
+    li.current a {
+      background: $menu_color;
+      font-weight: bold;
+    }
+  }
+}