[DRAFT, WIP] PSR-5: PHPDoc Standard

This PR represents the current state of affairs with the PHPDoc Standard. Until this description and subject is altered this PR is considered a Work in Progress and not ready for a final review.

All feedback is welcome, please direct this to the PHP-FIG mailing list to prevent noise in this PR. This PSR covers so many subjects that unless the discussions are separated by topic that it will probably be quite impossible to follow in this PR.

I would also request that people open a thread per issue they would like to discuss and not combine several issues in a single mail; this will help to keep noise-levels down in discussions and for me to loook back or filter important information.

TODO items are tracked in the issue tracker for this PSR: https://github.com/phpDocumentor/fig-standards/issues
Just for context from the WordPress side, we've been using hash-notations since last year using dollar signs. I agree the dollar sign is/will be important for parsability.

     * @param array $args {
     *     An array of query and display arguments.
     *
     *     @type int    $max     Number of posts to display.
     *     @type string $status  Post status.
     *     @type string $order   Designates ascending ('ASC') or descending ('DESC') order.
     *     @type string $title   Section title.
     *     @type string $id      The container id.
     * }