[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
Suggested rewrite of this paragraph:

---
The rules described above also apply to the inline version of this tag. The inline tag has two additional parameters that can be used to limit the lines of code to be shown.
---

Actually... you could probably just omit this paragraph. The text above already says all of this. No need to repeat it, and start the next paragraph with "For inline tags, "