handle nicely typical installation other than debian package / mercurial forest * new _find_prefix method to detect installation prefix (maybe specified using CW_INSTALL_PREFIX environment variable) * set various resource accessors according to this, cleanup on the way * remove no more necessary APYCOT_ROOT hacks

"""this contains the cube-specific entities' classes

:organization: Logilab
:copyright: 2001-2010 LOGILAB S.A. (Paris, FRANCE), license is LGPL v2.
:contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr
:license: GNU Lesser General Public License, v2.1 - http://www.gnu.org/licenses
"""