resolves #1573 - filetype icons and previews size

src/main/res/layout/list_item.xml

@@ -40,7 +40,7 @@
 
             <ImageView
                 android:id="@+id/thumbnail"
-                android:layout_width="32dp"
+                android:layout_width="@dimen/file_icon_size"
                 android:layout_height="@dimen/file_icon_size"
                 android:layout_centerInParent="true"
                 android:layout_marginLeft="8dp"

src/main/res/values/dims.xml

@@ -28,7 +28,7 @@
     <dimen name="nav_drawer_header_avatar_second_account_margin">56dp</dimen>
     <dimen name="nav_drawer_menu_avatar_radius">12sp</dimen>
     <dimen name="list_item_avatar_icon_radius">20dp</dimen>
-    <dimen name="file_icon_size">32dp</dimen>
+    <dimen name="file_icon_size">40dp</dimen>
     <dimen name="file_icon_size_grid">128dp</dimen>
     <dimen name="file_avatar_size">128dp</dimen>
     <dimen name="standard_padding">16dp</dimen>