Register Client-side library (as jquery, jquery-ui, bootstrap and other)

Single point of registration library
Include example of jquery library
The relationship between libraries registration

Use:
    
    $modx->regClientLib("bootstrap3");

or 

    $modx->regClientLib("jcarousellite,nivo-slider,jquery-ui,swfobject");

relationship. In bootstrap3/register.php

    ...
    $modx->regClientLib('jquery');
    ...

Can new option `lib` in snippets (example in  EvoGallery)

    //Подключаем библиотеки
    if (!empty($lib)){
        $modx->regClientLib($lib);
    }
The use of extract is a bad practice in my opinion. There is no real need for this, variables are introduced without a real definition and you always have to check where a later used variable name comes from.