[SPARK-2495][MLLIB] remove private[mllib] from linear models' constructors

This is part of SPARK-2495 to allow users construct linear models manually.

Author: Xiangrui Meng <meng@databricks.com>

Closes #1492 from mengxr/public-constructor and squashes the following commits:

a48b766 [Xiangrui Meng] remove private[mllib] from linear models' constructors
SPARK-2564. ShuffleReadMetrics.totalBlocksRead is redundant

Author: Sandy Ryza <sandy@cloudera.com>

Closes #1474 from sryza/sandy-spark-2564 and squashes the following commits:

35b8388 [Sandy Ryza] Fix compile error on upmerge
7b985fb [Sandy Ryza] Fix test compile error
43f79e6 [Sandy Ryza] SPARK-2564. ShuffleReadMetrics.totalBlocksRead is redundant
[SPARK-2552][MLLIB] stabilize logistic function in pyspark

to avoid overflow in `exp(x)` if `x` is large.

Author: Xiangrui Meng <meng@databricks.com>

Closes #1493 from mengxr/py-logistic and squashes the following commits:

259e863 [Xiangrui Meng] stabilize logistic function in pyspark
Improve scheduler delay tooltip.

As a result of shivaram's experience debugging long scheduler delay, I think we should improve the tooltip to point people in the right direction if scheduler delay is large.

Author: Kay Ousterhout <kayousterhout@gmail.com>

Closes #1488 from kayousterhout/better_tooltips and squashes the following commits:

22176fd [Kay Ousterhout] Improve scheduler delay tooltip.
[SPARK-1945][MLLIB] Documentation Improvements for Spark 1.0

Standalone application examples are added to 'mllib-linear-methods.md' file written in Java.
This commit is related to the issue [Add full Java Examples in MLlib docs](https://issues.apache.org/jira/browse/SPARK-1945).
Also I changed the name of the sigmoid function from 'logit' to 'f'. This is because the logit function
is the inverse of sigmoid.

Thanks,
Michael

Author: Michael Giannakopoulos <miccagiann@gmail.com>

Closes #1311 from miccagiann/master and squashes the following commits:

8ffe5ab [Michael Giannakopoulos] Update code so as to comply with code standards.
f7ad5cc [Michael Giannakopoulos] Merge remote-tracking branch 'upstream/master'
38d92c7 [Michael Giannakopoulos] Adding PCA, SVD and LBFGS examples in Java. Performing minor updates in the already committed examples so as to eradicate the call of 'productElement' function whenever is possible.
cc0a089 [Michael Giannakopoulos] Modyfied Java examples so as to comply with coding standards.
b1141b2 [Michael Giannakopoulos] Added Java examples for Clustering and Collaborative Filtering [mllib-clustering.md & mllib-collaborative-filtering.md].
837f7a8 [Michael Giannakopoulos] Merge remote-tracking branch 'upstream/master'
15f0eb4 [Michael Giannakopoulos] Java examples included in 'mllib-linear-methods.md' file.
[SPARK-2190][SQL] Specialized ColumnType for Timestamp

JIRA issue: [SPARK-2190](https://issues.apache.org/jira/browse/SPARK-2190)

Added specialized in-memory column type for `Timestamp`. Whitelisted all timestamp related Hive tests except `timestamp_udf`, which is timezone sensitive.

Author: Cheng Lian <lian.cs.zju@gmail.com>

Closes #1440 from liancheng/timestamp-column-type and squashes the following commits:

e682175 [Cheng Lian] Enabled more timezone sensitive Hive tests.
53a358f [Cheng Lian] Fixed failed test suites
01b592d [Cheng Lian] Fixed SimpleDateFormat thread safety issue
2a59343 [Cheng Lian] Removed timezone sensitive Hive timestamp tests
45dd05d [Cheng Lian] Added Timestamp specific in-memory columnar representation
Merge remote-tracking branch 'apache_spark/master'