The session fauna

Hi all,

Evolutions of Lenya for bring it to V3 is a very good opportunity to
clean, simplify and improve our code base.

As I work on the C2.2 migration (a first step), I figured out the
session fauna, we have :

- httpsession
- cocoon sessions (seems that each servlet protocol create a new one)
- o.a.l.cms.repository.SessionImpl
- o.a.l.cms.publication.SessionImpl
- session retrieved from spring context
- maybe some others...

This fauna imply a multiple ways to access the "session" (near each by
class) and confusing a lot.

IMO a good solution will be to provide a "frontier" class that provide
to all lenya code a unique way to access session and deal with
"externals" (spring, cocoon, http,...) sessions.

Another point is witch objects hold the session ? the repository, the
publication, the user ?

??

++