shell not present in /etc/shells

Cherry-pick of cca1a120

Conflicts:

	slapos/recipe/generate_erp5_tidstorage.py

software.cfg

Additionaly this selects different lxml egg, and "disables" lxml building hack.
Signed-off-by: Cédric de Saint Martin <cedric.dsm@tiolive.com>

This add also dependency to inotifyx in order to have a better
mechanism for file system watching.

I choose inotifyx because the api is much more simpler.