Table in README + Direct Download links + pdfs/ directory

A small patch built on top of @stevana's reorganizing the README and the repository:

* The pdfs are now in a dedicated directory (the README is therefore visible immediately)
* The papers are now presented in a table (the dates where previously scatered around at the end of the lines)
* Links are now offering direct download of pdfs rather than landing on a weird github page offering to view the raw content