SPARK-5665 [DOCS] Update netlib-java documentation

I am the author of netlib-java and I found this documentation to be out of date. Some main points:

1. Breeze has not depended on jBLAS for some time
2. netlib-java provides a pure JVM implementation as the fallback (the original docs did not appear to be aware of this, claiming that gfortran was necessary)
3. The licensing issue is not just about LGPL: optimised natives have proprietary licenses. Building with the LGPL flag turned on really doesn't help you get past this.
4. I really think it's best to direct people to my detailed setup guide instead of trying to compress it into one sentence. It is different for each architecture, each OS, and for each backend.

I hope this helps to clear things up 

Author: Sam Halliday <sam.halliday@Gmail.com>
Author: Sam Halliday <sam.halliday@gmail.com>

Closes #4448 from fommil/patch-1 and squashes the following commits:

18cda11 [Sam Halliday] remove link to skillsmatters at request of @mengxr
a35e4a9 [Sam Halliday] reword netlib-java/breeze docs