Don't overwrite config if createConfigurator was called several times

[tadatuta]

createConfigurator() when called in a loop is overwritten now:

platforms.forEach(function(platform) {
    config.module('enb-bem-docs')
        .createConfigurator('docs', 'examples')
        .configure({
            levels: levels,
            destPath: path.join(destFolder, lib, platform + '.docs'),
            exampleSets: [path.join(destFolder, lib, platform + '.examples')],
            langs: config.getLanguages(),
            jsdoc: { suffixes: ['vanilla.js', 'browser.js', 'js'] }
        });
});

It would be great to add new declarations (or at least log warns to console) in such occasions.