[SPARK-2864][MLLIB] fix random seed in word2vec; move model to local

It also moves the model to local in order to map `RDD[String]` to `RDD[Vector]`.

Ishiihara

Author: Xiangrui Meng <meng@databricks.com>

Closes #1790 from mengxr/word2vec-fix and squashes the following commits:

a87146c [Xiangrui Meng] add setters and make a default constructor
e5c923b [Xiangrui Meng] fix random seed in word2vec; move model to local
[SPARK-2503] Lower shuffle output buffer (spark.shuffle.file.buffer.kb) to 32KB.

This can substantially reduce memory usage during shuffle.

Author: Reynold Xin <rxin@apache.org>

Closes #1781 from rxin/SPARK-2503-spark.shuffle.file.buffer.kb and squashes the following commits:

104b8d8 [Reynold Xin] [SPARK-2503] Lower shuffle output buffer (spark.shuffle.file.buffer.kb) to 32KB.
[SPARK-2550][MLLIB][APACHE SPARK] Support regularization and intercept in pyspark's linear methods

Related to Jira Issue: [SPARK-2550](https://issues.apache.org/jira/browse/SPARK-2550?jql=project%20%3D%20SPARK%20AND%20resolution%20%3D%20Unresolved%20AND%20priority%20%3D%20Major%20ORDER%20BY%20key%20DESC)

Author: Michael Giannakopoulos <miccagiann@gmail.com>

Closes #1775 from miccagiann/linearMethodsReg and squashes the following commits:

cb774c3 [Michael Giannakopoulos] MiniBatchFraction added in related PythonMLLibAPI java stubs.
81fcbc6 [Michael Giannakopoulos] Fixing a typo-error.
8ad263e [Michael Giannakopoulos] Adding regularizer type and intercept parameters to LogisticRegressionWithSGD and SVMWithSGD.