add service for configure labels text

Add provider for allow configure labels text (Select all, Select none, etc)
Example of usage for localize to russian language

    angular
        .module('app', ['ngGrid', 'multi-select'])
        .config(function (MultiSelectLabelsProvider) {
            MultiSelectLabelsProvider.setLabels({
                selectAllButtonLabel: "Выделить все",
                selectNoneButtonLabel: "Снять со всех",
                resetButtonLabel: "Сбросить",
                totalLabel: "Выбрано",
                noneLabel: "Ничего не выбрано"
            });
        })