[SPARK-2358][MLLIB] Add an option to include native BLAS/LAPACK loader in the build

It would be easy for users to include the netlib-java jniloader in the spark jar, which is LGPL-licensed. We can follow the same approach as ganglia support in Spark, which could be enabled by turning on "-Pganglia-lgpl" at build time. We can use "-Pnetlib-lgpl" flag for this.

Author: Xiangrui Meng <meng@databricks.com>

Closes #1295 from mengxr/netlib-lgpl and squashes the following commits:

aebf001 [Xiangrui Meng] add a profile to optionally include native BLAS/LAPACK loader in mllib