File Attributes should be typed as Guid rather than object

[daryllabar]

Currently File Column attributes are being generated as objects, even though they are actually GUIDS.

[Microsoft.Xrm.Sdk.AttributeLogicalNameAttribute("acme_file")]
public object Acme_File
{
	[System.Diagnostics.DebuggerNonUserCode()]
	get
	{
		return this.GetAttributeValue<object>("acme_file");
	}
}