install.php needs to be invoked by packages.php

Specific installers classes are now put in 'modules/installers' and
included by using PHP __autoload() method.
PsexecRemoteInstaller file

Implementation of a Windows to Windows installer.
config.php defines my_session_() method and other stuff

my_session_() method helper to avoid starting sessions if command was
invoked by command-line.
Defined FROM_PACKAGES

Function isCommandLineInterface() moved to config.php
my_session_("start") is now session_start() equivalent
-n option added to php-cgi command line
Constants moved to config.php