Created Issue: 4.0 beta, Form Markup parsing fail if namespaces are declared below cms:layout [1672]

Repro:

Make a data type and have the following form markup for some field:

```
<KeySelector Label="Brand" Help="" OptionsKeyField="Id" OptionsLabelField="Title" Required="true">
<KeySelector.Selected>
<cms:bind source="Brand" />
</KeySelector.Selected>
<KeySelector.Options>
<f:function xmlns:f="http://www.composite.net/ns/function/1.0" name="Composite.Data.Types.IPage.GetIPageXml">
<f:param name="PropertyNames">
<f:paramelement value="Id" />
<f:paramelement value="Title" />
</f:param>
</f:function>
</KeySelector.Options>
</KeySelector>
```

Try rendering the form (add/edit data). This will give the error "The producer Composite.Functions.Forms.FunctionProducer does not have property named f"

__Workaround:__ Removing the namespace declaration (moving it to the document root element) fix this issue.

The issue is that namespace declarations are handled as normal attributes - they should not.