Animate

Hi Max, first integration of animation system with dreem, ready for review
This is missing a comment so the docs work, something like:
  <!--/**
     * @class dr.animator {Animation}
     * @extends dr.node
     * An animator
     *
     *     @example
     *     <ace id="editor" width="500" text='Hello World'></ace>
     *
     * The initial text can also be included inline, and include dreem code.
     *
     *     @example wide
     *     <ace id="editor" width="500"><view width="100%" height="100%" bgcolor="thistle"></view></ace>
     *
     */-->