this still needs further clean up, is to say consolidation.
also, Five needs to be fixed regarding its (very funky) usage of Expressions.py

Basically, zope.app's path expressions use ITraversable adapters to
traverse through the object graph. This is the only sane thing to do,
really. However, we still want to take care of Zope2's OFS.Traversable
which most promimently allowes the __bobo_traverse__ hook.  (The irony
is that OFS.Traversable uses Zope 3-style *URL* traversal these days;
yes, *URL* traversal, not *object graph* traversal).

Still confused?

Basically, if we encounter something that is OFS.Traversable'ish, use
restrictedTraverse. Use Zope3-style object graph traversal in all other
cases....

correct argument order in useful implementation

Fixes issue with AcceleratedHTTPCacheManager sending PURGE from a 
virtual-hosted zope, and adds a bunch of related tests and comments.

for strings, i believe...

ProductDispatcher's __bobo_traverse__ now checks all products registered in Control_Panel.Products rather than simply checking the python Products namespace package.

spaces.

and a corresponding Five trunk

Merge from svn+ssh://regebro@svn.zope.org/repos/main/Zope/branches/regebro-wsgi_support2