Added Basic, Fortran and xBase categories.

With a few links each to kick starting them.
Update free-programming-books.md
Merge pull request #493 from DrDub/master

Added Basic, Fortran, xBase Books and Cats. + 1Fix
Update free-programming-books-ko.md

fix indent
Merge pull request #494 from minsOne/patch-1

Update free-programming-books-ko.md
Adding Erlang Handbook to English list
adding pdf description to erlang handbook entry
Merge pull request #495 from jboverfelt/master

Adding Erlang Handbook
fix link
Merge pull request #496 from johand/fix_link

fix link
Added to Open Source Ecosystem: The Art of Community, Open Advice, The Wealth of Networks.
Merge pull request #497 from shelleyvadams/master

Added 3 books to Open Source Ecosystem
Quick fix to fa_IR index
Added JavaScript Garden book to languages *es*, *ko*, *pl* and *tr*.
Added "Git Magic" to languages *de* and *ru*
Added a popular CSS book to the languages *es*, *fa-IR*, *fr* and *pt-PT*.
Add OpenCL Programming Book and move HPC links to Parallel section
Merge pull request #498 from jgpacker/master

Added some book's translations to different languages
Merge pull request #499 from corburn/master

Add OpenCL Programming Book and move HPC links to Parallel section
don't commit to a large amount of unrelated changes for different/similar files