[development] Move all core modules into their own directories.

[Khalid B]

A  previous discussion that points to previous discussions.

http://lists.drupal.org/archives/development/2006-03/msg00134.html

Ber had some great RoR inspired ideas that expanded on mine,
and Morbus had some other good ideas too.

The issues are:
- Security (keep non data files out of  DocumentRoot)
- Upgradability (isolation of core Drupal from user modified files)
- Easier backups (Cleaner directory structure)
- Some other points mentioned in the above threads.

(Normally at this point, we start seeing the "CVS sucks",  "SVN
is the way to go", "No bzr is ...", ...etc., but as Gabor said,  it is
a solved issue, so please leave those for another slower day on the
mailing list.)