Add non-generic EnumDehumanizeExtensions.DehumanizeTo

[JeremyThomas]

I could use a non-generic EnumDehumanizeExtensions.DehumanizeTo for when the enum type isn't known at compile time.

I wrote my own which I use in my HumanizedEnumConverter:
https://rapiddevbookcode.codeplex.com/SourceControl/latest#LLBL Pro v4.1/AW.Helper/TypeConverters/HumanizedEnumConverter.cs

e.g.

    private static Enum DehumanizeTo(string input, Type enumType)
    {
      var values = Enum.GetValues(enumType);
      foreach (var value in values)
      {
        var enumValue = value as Enum;
        if (enumValue == null)
          return null;
        if (string.Equals(enumValue.Humanize(), input, StringComparison.OrdinalIgnoreCase))
          return enumValue;
      }
      return null;
    }

[MehdiK]

Thanks - yeah I think that could be useful at times.

I would appreciate if you could please review #93 for this.