Add example with solution_dict and substituting in a matrix

[kcrisman]

See  this ask.sagemath.org question. The poster wants an example something like

f(x,y)=x^2*y+y^2+y
solutions=solve(list(f.diff()),[x,y])
the_solution=solutions[2]
H=f.diff(2);  # Hessian matrix

but showing this.

sage: solutions=solve(list(f.diff()),[x,y],solution_dict=True)
sage: solutions
[{y: 0, x: -I}, {y: 0, x: I}, {y: -1/2, x: 0}]
sage: H.subs(solutions[2])
[(x, y) |--> -1  (x, y) |--> 0]
[ (x, y) |--> 0  (x, y) |--> 2]
sage: H(x,y).subs(solutions[2])
[-1  0]
[ 0  2]

This seems like a reasonable request.