[WIP] [MLLIB] Ordinary least square implementation

[falaki]

This is work in progress

Along with other statistical summaries we are interested in getting summary statistics for a linear regression model:

• Standard deviation of estimated parameters
• t-statistic and p-value for testing if estimated parameters may be equal to zero
• R-squared and Adjusted R-squared
  Also possibly:
• AIC
• Leverage

We will be using SVD to solve the OLS and estimate above statistics.

[SparkQA]

QA tests have started for PR 1560. This patch merges cleanly.
View progress: https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder/17086/consoleFull

[SparkQA]

QA results for PR 1560:
- This patch FAILED unit tests.
- This patch merges cleanly
- This patch adds the following public classes (experimental):
class OrdinaryLeastSquares extends Optimizer with Logging {

For more information see test ouptut:
https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder/17086/consoleFull

[pwendell]

Let's close this issue pending an update from @falaki .