Loading enum-typed formatter settings from .csproj files fails

When loading formatter settings from project files, elements like

```
<SerializedObject key="ElseNewLinePlacement">
    <NewLinePlacement xmlns="clr-namespace:ICSharpCode.NRefactory.CSharp;assembly=ICSharpCode.NRefactory.CSharp">SameLine</NewLinePlacement>
</SerializedObject>
```

are not deserialized correctly (enum type can't be resolved). This works for global settings and solutions, though.
