Parallel and Concurrent Programming in Haskell is now hosted on O'Reilly Safari.

* Added an OpenGL book to the Finnish list

* Added missing newlines and a translation

CA-Clipper 5.2 Norton Guide is not available anymore since last May, according to Archive.org and the nameserver changes made at the time. I changed the link to point to the latest archived page which seems to have quite a good coverage.

Removed the link to O'Reilly Commons because it doesn't exist anymore.

* Update free-programming-books-bl.md

* Update free-programming-books-bl.md

* Update free-programming-books-bl.md

* Update free-programming-books-bl.md

* Update free-programming-books-bl.md

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* Update free-programming-playgrounds.md

* Update free-programming-playgrounds.md

backbone js book was duplicated in js and backbonejs section so I removed it from js section (#3460)

* Added Snap! Reference Manual

* Fix link

* Fixed build error

Ruby User's Guide was pointing to a "Page not found" location (as described in issue #3448 ) but ruby-doc.org hosts almost 1:1 version of that same document so I updated the link to point there.

* Added "High Performance Accelerated Websites" book

* Updated order

* Added MOOC: openSAP

* Update free-programming-books.md

Added the book "SAP Code Style Guides - Clean ABAP", which is an adoption of Robert C. Martin's "Clean Code" for the language ABAP. The license is CC BY 3.0.

* Add Software Architecture Reactive Microsystems: The Evolution of Microservices

* fixed linter