Removed document.ready dependency, and facilitated adding elements at runtime

The call to <b>$(document).ready()</b> was causing bugs where the Ribbon might not have been initialized correctly if <b>Init()</b> was not called yet. This was fixed by making <b>Init()</b> responsible of adding classes and handlers.

In addition, the <b>InitElement()</b> was introduced to allow runtime initialization of dynamically created elements within the Ribbon.