* added classes that represent different name kinds
* rewrote NameResolvers to return the new name classes instead of NameElement and NameHierarchy
* removed DataType classes since their functionality moved to the CxxTypeName class.
* moved source code for solving names of NestedNameSpecifiers to new CxxSpecifierNameResolver.
* implemented recording of UsingDirectives.
* implemented using file as context for using directives and using directive decls if no other context is available.
* re-implemented recording of the auto keyword