-add set...() methods and their documentation; remove Generic

-use row-major traversal when the number of columns is fixed
 and the number of rows is dynamic
-other minor changes

test/map.cpp

@@ -31,7 +31,7 @@ template<typename VectorType> void tmap(const VectorType& m)
 {
   typedef typename VectorType::Scalar Scalar;
   
-  int size = m.coeffs();
+  int size = m.size();
   
   // test Map.h
   Scalar* array1 = new Scalar[size];