Added ability to DataTableVm class to set custom JS options

Usage:

var vm = Html.DataTableVm("table-id", (HomeController h) => h.GetUsers(null));
vm.JsOptions.Add("iDisplayLength", 25);
vm.JsOptions.Add("aLengthMenu", new object[] { new[] {5, 10, 25, 250, -1} , new object[] { 5, 10, 25, 250, "All"} });