New proof of Lemma 0032
Merge branch 'dbergh-master'

New proof of Lemma 0032 by Daniel Bergh

A new proof for the lemma about colimits indexed filtered categories
as colimits indexed by partially ordered sets. The proof is maybe
slightly too long. It could be shortened by doing any of these things:

Split the Lemma in two. One which asserts the existence of a cofinal
functor I_0 -> I and corollary using a formulation in terms of systems.

The definition of cone and cocone could be moved to the section about
limits (002D)

The definition of finitely generated category could be moved to the
section about finite limits a colimits (04AS). Also this notion
occurs in Lemma 05XU

The fact that any finite (finitely generated) diagram in a filtered
category has a cocone could be stated as a separate lemma in the
section about filtered categories (04AX).

The statement that a product of filtered categories is filtered could
be stated as a separate lemma.

The statement that compositions of cofinal functors are cofinal could
be stated as a separate lemma.
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