More explicit universe manipulation

One effective way to implement side effects in a purely functional language is
to represent the universe as a first class data type. Traditionally, this data
type is then hidden behind a layer of abstraction called a monad, to make it
easier to program.

We investigate what sort of programming models one can achieve by removing the
monad. That is to say, we manipulate the universe directly. This leads to a
number of interesting cases, including cases where multiple universes may exist
at once (i.e. a multiverse). We show limitations of existing implementations,
and show how a number of interesting approaches can be allowed for by true first
class universe data types.