matrix storage order can now also be row-dominant (choosable for each matrix separately)

map() moves from MatrixBase to Matrix
much more documentation/examples/snippets

doc/snippets/MatrixBase_eval.cpp

@@ -0,0 +1,12 @@
+Matrix2f M = Matrix2f::random();
+Matrix2f m;
+m = M;
+cout << "Here is the matrix m:" << endl << m << endl;
+cout << "Now we want to replace m by its own transpose." << endl;
+cout << "If we do m = m.transpose(), then m becomes:" << endl;
+m = m.transpose();
+cout << m << endl << "which is wrong!" << endl;
+cout << "Now let us instead do m = m.transpose().eval(). Then m becomes" << endl;
+m = M;
+m = m.transpose().eval();
+cout << m << endl << "which is right." << endl;