Change distro to distrolib

Current distro file "publish" config variables as globals. That's ugly.

Also, we need one hook before database creation by installer, because windows packages use to change the password (default to blank in xampp) to the entered one.

So I'm going to:

1) Change current use of distro.php to call to: distro_get_config() function
2) Add hook distro_pre_create_db() before database creation
3) Both functions will be executed if exist
4) distrolib.php will be included_once() if exists.

Agreed with Petr (adding him as QA). Ciao