[#1375] Add script to initialize windows build environment.

Problem description
===================
    To build the projects on windows platform some steps need to be follow in
order to have the prerequisites installed :

-    download and install msys
-    download and install git
-    install msys-wget
-    modify the profile in msys
-    create "chevah" directory
-    run bash from msys or git 

    In order to simplify the process and to resolve some conflicts between msys and git, a script was created. The script will take care of the above steps. Nothing will be installed in the system; needed packages are installed in the user's home directory.
    Git and msys-wget have been merged into one zip archive and stored on binary.chevah.com server. When the script is executed first time it will download the archive and unpack it to ~/chevah/mingw/git directory.

Next time when the script is executed it will open an console with bash.

    The script also supports basic updating. In order to update the version from the script must be modified. The version must be the same with that from the server.


Why we got into this (5 whys)
=============================

In order to simplify the process and to resolve some conflicts between
msys and git.


Changes description
===================

Implement a script that automates the required steps.


How to try and test the changes
===============================

reviewers @adiroiban @alibotean

Execute the script on windows and all the prerequisites should be in ~/chevah.