Overloads norm using graph representation or integer reprsentation

```
y = norm(x)
y = norm(x,1)
y = norm(x,2)
y = norm(x,inf)
y = norm(x,'fro')
y = norm(x,'nuclear') % Schatten 1-norm, Ky-Fan, alternatively norm(x,'*')
y = norm(x,fractional_number)
```

The operator is implemented using a graph representation based on a linear, second-order cone, or semidefinite programming model, depending on the choice of norm (second argument), and can thus only be used in scenarios where YALMIP can propagate convexity. For fractional norms, pnorm is automatically used.

Structured nonconvex scenarios are only supported for norms with second argument **1** and **‘inf’** (leading to an integer representation). For other cases, use general nonlinear constructs with sqrtm and powers etc to define the expression.