Add support for fluid doc

Fluid doc

Actually it is not possible to add docs like php doc. If you have a partial for instance it will be really awesome if the partial knows which parameters are passed thru and for which the partial is used.

So the idea is to introduce something like php doc for fluid. You only need to add the documentation within a <f:comment>. Otherwise the documentation will be rendered.

<f:comment>
  // This partial is used for render a single blog post.
  //
  // @param {object} user
  // @param {object} post
  // @return {string}
</f:comment>
<f:render partial="BlogPost" arguments="{user: user, post: blog.post}" />

The notiation of the comment is just an example and can be discussed by the community.

If you edit such documentation you can show the documentation within intelij as doc and the Fluid plugin is able to validate the variables in the partial.