Add support to track multiple tracker id from one snippet

[michalsikora]

Currently we have snippet with hardcoded tracker id

<script type="text/javascript">
    (function (w, d, t, g, u) {
        w[g]=w[g]||function(){(w[g].q=w[g].q||[]).push(arguments);};
        var tag=d.createElement('script');
        tag.async=true;tag.src=u+'?g='+g+'&t='+t;
        var s=d.getElementsByTagName('script')[0];
        s.parentNode.insertBefore(tag, s);
    }(window, document, 'WEBA-0001', 'weba', '//example.com/path.to.tracker.js'));
</script>

And the thing is to remove tracker id from snippet eg: 'WEBA-0001' and move logic outside.
Below one of possibilities to implement:

weba('create', {
    name: 'firstTracker',
    trackerId: 'WEBA-01'
});
weba('firstTracker.send', {
    event: 'pageView'
});

weba('create', {
    name: 'secondTracker',
    trackerId: 'WEBA-02'
});
weba('secondTracker.send', {
    event: 'pageView'
});

For one tracker it should work like this:

weba('create', {
    name: 'onlyOneTracker',
    trackerId: 'WEBA-01'
});
weba('send', {
    event: 'pageView'
});