Daemon cleanup does not record initial state of global environment

[shikokuchuo]

As identified by @noamross in #90 (comment),:

daemon() cleanup does not currently restore objects in the global environment to an initial state - as the initial state is not recorded.

Instead, it is incorrectly assumed that .Random.seed is the only object.

This is not necessarily the case if

(i) it is called interactively with objects already in the global environment, or
(ii) these are created by R startup files such as .Rprofile.