[Seaside] swapping root components

[radoslav hodnicak]

Currently I'm playing with iframes and it is convenient to store the
session's root component in a state holder instead of the instvar. This
way all the iframes work within the same session and have own root
components - set on the fly. This is useful to create print previews etc
too.

The changes to seaside (2.3) were minimal and so far it's working ok, any
bad surprises that could wait for me?

Regards, radoslav
-- 
pgp.mit.edu  0x30DEBAE6  12EE FED5 D5B1 77ED 5637 EB77 2A5F 22F9 30DE BAE6