[Feature] Allow methods for Dropdown

[WazWaz]

I'm using this workaround:

    [Dropdown("TheValues")]
    public int foo;
    public static DropdownList<int> TheValues = ValuesFunction();

    DropdownList<int> ValuesFunction()
    {
        for (...) ...
    }

But it would be nicer to write:

    [Dropdown("ValuesFunction")]
    public int foo;
    ...

(or "ValuesFunction()").