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 ActivityTool.activateObject() public.

so that we can register activity by path from restricted environment.
also set default parameters just same as ActiveObject.activate().
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>