put activity_tool and request values in ActiveWrapper.

so that we can call ActivityTool.activateObject() with not only by
object but also by it's path.

Signed-off-by: Vincent Pelletier <vincent@nexedi.com>
make zsqlbrain's activate() return an ActiveWrapper object without calling getObject().

With this change, code like the following will use much less memory.

  for i in portal_catalog(...):
    i.activate().method()

Signed-off-by: Vincent Pelletier <vincent@nexedi.com>