Documentation: Minor fix for the PCA docs

This fixes some typos in the PCA documention.
Documentation: Change format for multiple modules

- Changed the documentation format for following modules:
    - Multilogistic Regression
    - Summary
    - Correlation
    - Cox Proportional Hazards
Documentation: Add note about table names and other corrections

- Updated description file to remove "Beta" statement
- Added a note about table and column names requiring double quoting
if name is case-sensitive or contains multibyte characters.
- Changed all the argument types to be succint.
- Made significant updates to the Linear System documentation to
correct many errors.
Abstraction layer: Change setp to this->setp

- Upgrading gcc to 4.7 leads to the following error:
../src/dbal/OutputStreamBufferBase_impl.hpp:75:9: error: 'setp' was
not declared in this scope, and no declarations were found by
argument-dependent lookup at the point of instantiation [-fpermissive]
../src/dbal/OutputStreamBufferBase_impl.hpp:75:9: note: use 'this->setp' instead

- Making that change fixes the problem
Doxygen: Update user and developer doxygen settings

Changes:
    - New tags were added for "Online Help" and "Output"
    - Collaboration and class graphs removed from user doc
    - External file lists removed from user doc
SVEC: Add out-of-bounds check even if size=0
Multilogistic: Ensure names are same between Python and SQL

- Change in multilogistic sql_in function for documentation led to
difference in the name of a parameter in SQL and corresponding python
function.
Multilogistic: Missed one name change
Documentation: Change doxygen build process

Doxygen build modifications:
    - Update doxygen requirement to 1.8.4
    - Add custom header.html with MADlib keywords and links to previous versions
    - Add custom madlib_extra.css with custom CSS
    - No colons on headers anywhere
    - Remove CSS patch and include that content in custom CSS file
    - Increase font size in TOCs
    - Enable markdown processing
    - add keywords to docs
    - increase toc.li font size
    - remove Files from topics
    - remove diagram
    - define src/images directory
- Reformat various modules to reflect doxygen changes
New Module: Timeseries analysis using ARIMA modeling

Pivotal Tracker: 54248646

Additional authors:
    Shengwen Yang <syang@gopivotal.com>
    Rahul Iyer <riyer@gopivotal.com>

Module includes:
    - Training an ARIMA model for non-seasonal univariate time series
    data
    - Forecasting future values in the time series using trained model
    - Grouping and seasonal data are currently not supported and
    are planned for future work
Documentation: Update ARIMA doc to new format
Release steps: Update release notes and other version numbers
Upgrade from v1.0/v1.1 to v1.2
Support time stamps other than integers starting from 1
Documentation: Multiple changes to doc format

- Removed "Files" node from the left panel and allows to customize the
contents of the left panel by editing DoxygenLayout.xml.
- ARIMA: Reformated syntax to one arg per line and add results to
 example.
- Other modules:
    - Syntax arguments one per line, changed presentation of defaults
    - Revised menus, syntax, arguments, examples for consistency.
    - Corrected misspelling and other typos