adds the max_attachment_size_kb setting

so that we can specify a different max upload size for attachments and images.

spec/models/site_setting_spec.rb

@@ -88,4 +88,26 @@ describe SiteSetting do
     end
   end
 
+  describe "authorized extensions" do
+
+    describe "authorized_uploads" do
+
+      it "trims space and adds leading dots" do
+        SiteSetting.stubs(:authorized_extensions).returns(" png | .jpeg|txt|bmp")
+        SiteSetting.authorized_uploads.should == [".png", ".jpeg", ".txt", ".bmp"]
+      end
+
+    end
+
+    describe "authorized_images" do
+
+      it "filters non-image out" do
+        SiteSetting.stubs(:authorized_extensions).returns(" png | .jpeg|txt|bmp")
+        SiteSetting.authorized_images.should == [".png", ".jpeg", ".bmp"]
+      end
+
+    end
+
+  end
+
 end