[Issue Type] DefaultMember is migrated into MDX script [Issue Description] 
In previous versions of Analysis Services, the default member of a dimension is specified by a Multidimensional Expressions (MDX) expression, contained in the DefaultMember property of the dimension. In Microsoft SQL Server 2005 Analysis Services (SSAS), this property was replaced by functionality supported in MDX scripts, and the property is upgraded to a MDX script during migration.