SPARK-4022 [CORE] [MLLIB] [WIP] Replace colt dependency (LGPL) with commons-math

This change replaces usages of colt with commons-math3 equivalents, and makes some minor necessary adjustments to related code and tests to match.
The default RNG is Well19937c. From the doc, it is better but slower than MT. I'm leaning towards the default because sampling computation is usually not the bottleneck for Spark.