This contribution is my original work and I license it to the project under it's open source license.

Author: jose.cambronero <jose.cambronero@cloudera.com>

Closes #6994 from josepablocam/master and squashes the following commits:

bbb30b1 [jose.cambronero] renamed KSTestResult to KolmogorovSmirnovTestResult, to stay consistent with method name
0d0c201 [jose.cambronero] kstTest -> kolmogorovSmirnovTest in statistics.md
1f56371 [jose.cambronero] changed ksTest in public API to kolmogorovSmirnovTest for clarity
a48ae7b [jose.cambronero] refactor code to account for serializable RealDistribution. Reuse testOneSample( _, cdf)
1bb44bd [jose.cambronero]  style and doc changes. Factored out ks test into 2 separate tests
2ec2aa6 [jose.cambronero] initialize to stdnormal when no params passed (and log). Change unit tests to approximate equivalence rather than strict
a4bc0c7 [jose.cambronero] changed ksTest(data, distName) to ksTest(data, distName, params*) after api discussions. Changed tests and docs accordingly
7e66f57 [jose.cambronero] copied implementation note to public api docs, and added @see for links to wiki info
e760ebd [jose.cambronero] line length changes to fit style check
3288e42 [jose.cambronero] addressed style changes, correctness change to simpler approach, and fixed edge case for foldLeft in searchOneSampleCandidates when a partition is empty
9026895 [jose.cambronero] addressed style changes, correctness change to simpler approach, and fixed edge case for foldLeft in searchOneSampleCandidates when a partition is empty
1226b30 [jose.cambronero] reindent multi-line lambdas, prior intepretation of style guide was wrong on my part
9c0f1af [jose.cambronero] additional style changes incorporated and added documentation to mllib statistics docs
3f81ad2 [jose.cambronero] renamed ks1 sample test for clarity
992293b [jose.cambronero] Style changes as per comments and added implementation note explaining the distributed approach.
6a4784f [jose.cambronero] specified what distributions are available for the convenience method ksTest(data, name) (solely standard normal)
4b8ba61 [jose.cambronero] fixed off by 1/N in cases when post-constant adjustment ecdf is above cdf, but prior to adj it was below
0b5e8ec [jose.cambronero] changed KS one sample test to perform just 1 distributed pass (in addition to the sorting pass), operates on each partition separately. Implementation of Sandy Ryza's algorithm
16b5c4c [jose.cambronero] renamed dat to data and eliminated recalc of RDD size by sharing as argument between empirical and evalOneSampleP
c18dc66 [jose.cambronero] removed ksTestOpt from API and changed comments in HypothesisTestSuite accordingly
f6951b6 [jose.cambronero] changed style and some comments based on feedback from pull request
b9cff3a [jose.cambronero] made small changes to pass style check
ce8e9a1 [jose.cambronero] added kstest testing in HypothesisTestSuite
4da189b [jose.cambronero] added user facing ks test functions
c659ea1 [jose.cambronero] created KS test class
13dfe4d [jose.cambronero] created test result class for ks test