Logistic regression: Print message when grouping is not NULL

The message of "# groups succesfully passed, and # groups failed"
should be printed when grouping_str is not NULL. Previously, there
was a typo here and "not" was missing.
Logistic Regression: Grouping for text columns

Changes:
    - Added new check to ensure that all grouping values are "quoted" before
        cast to 'text' except for NULL/None
    - Cleaned up most of the python validation
    - Changed version to 0.7dev
Logistic Regression: Handle grouping in lower PG/GP versions

The previous commit handled grouping columns with type text by adding quotes to
grouping values, except for NULL values. Lower versions of PG and GP, however,
add quotes to all values using array_to_string skipping the NULL exception.
This commit handles that case by explicitly looking for 'null' in the group
values.
Logistic regression: Correct problems with install-check

- Corrected the accidental clobering of an if-statement
- Corrected missing assert statement in install-check
Python group controller: Strip double quotes in _string_to_array output
New module: Correlation

- Created a correlation module that computes the coefficient of correlation
between various numeric columns of a relation.
New module: Upgrade

Added new functionality to upgrade MADlib deployment on a database without
removing the previous installation. This is currently only supported for version
0.5 and greater. We don't yet support upgrade in Postgresql systems since
MADlib installs a Bool-to-Text cast in Greenplum and the upgrade tries to drop
the cast. This leads to a problem in Postgresql and should be handled as an
exception in future releases.
Correlation: Ensure duplicate target column names are handled

Other changes:
- Updated help message to reflect changes in output table format
- Updated output message before correlation is started
Release v0.7 tasks: Update version, add release notes and tags
Correlation: Fix formating problems with documentation
Release Packaging: Fix problems with RPM and GPPKG

RPM and GPPKG did not install in the Versions/ folder. This commit fixes that
problem
Fix for upgrade search path
ReleaseNotes: Add warning about problems in upgrade
Summary: Fix problems with out-of-memory for many columns

JIRA: Pivotal-170, 171

Pivotal-170: When running 'summary' on a large number of columns,
the quartile computation ends of consuming high amount of memory. This
has been resolved by splitting the actual columns into reasonable set
of columns, and returning the final output by colating results for each
set.

Pivotal-171: Wrong results are produced when the target_columns set
contains more than one column and all values in a column are NULL.
This is caused by the odd behaviors of "select
string_to_array(unnest(x_array), 'delim')": when x_array contains NULL
values, it will produce different results from "select
string_to_array(value, 'delim') from unnest(x_array) as value".
This has been resolved by moving the unnest call to a subquery.
Linear Algebra: Add new module for sparse/dense matrix multiplication

Sparse matrices are represented as <row, col, val> column triplets in
a table. Dense matrices are either of the form <row, ARRAY[]> or
<row, col1, col2, col3 ...>. This module enables the multiplication of
matrices where the left and right matrix can be of any of the sparse or
dense forms.
Added robust estimator for linear and logistic regressions and

Cox and right-sensoring
Merged to integration
Conflicts:
	src/modules/regress/LinearRegression_impl.hpp
	src/modules/regress/LinearRegression_proto.hpp
	src/modules/regress/linear.cpp
	src/modules/regress/logistic.cpp
	src/ports/postgres/modules/regress/linear.sql_in
	src/ports/postgres/modules/regress/logistic.sql_in
	src/ports/postgres/modules/regress/robust.sql_in
	src/ports/postgres/modules/regress/test/robust.sql_in
Set the category 0 as the reference category to be consistent with R.nnet

Make the signs of coefficients to be consistent with R.nnet

Remove numcategories parameter and add ref_category parameter

Update unit tests

Add prefix __ to internal functions and add STRICT to public functions

Add more parameter checking
Regress: Separation of the robust variance function call

The robust variance function call was split into two different
functions.  One for linear regression, and one for logistic regression.
In addition, their are several bug fixes for grouping support in the
linear and logistic regression.
Elastic Net: Minor corrections in documentation

PivotalTracker: 52239115

Updates to documentation:
    - Corrected the placement of '*' in independent instead of dependent
    - Reformated various lists of parameters