this merge contains:
* a new plugin architecture
* a pluginized pytest core
* many pytest related refactorings
* refactorings/streamlining of pytest's own tests
--HG--
branch : trunk
* moving in test, misc, code, io directories and
py/__init__.py
* py/bin/_find.py does not print to stderr anymore
* a few fixes to conftest files in other dirs
some more fixes and adjustments pending
--HG--
branch : trunk
hpk