Remove unnecessary structure bracketting

As per 89fc99bc3, but on as many examples as a grep -R can find.

Avoid warning message when deleting some constants.

do not export constant t0 from wotTheory

I get the impression that none of the definitions in wotTheory were
supposed to be exported, so perhaps they all should be deleted at the
end. I am not sure, though, so I just remove t0, whose name is
particularly annoying outside this theory to be taken by a constant.

Remove calls to print_theory in enumfset/script files.

print_theory is fine to call interactively, but just adds verbiage
when done as part of a build. Having done a build, looking at a
Theory.sig file is a good way to see what one has achieved.

Move some results from enumfset earlier into relationTheory.

Latest updates to enumfset code (from Lockwood Morris).

Builds on master.

New 'enumerated finite set library' by Lockwood Morris. (As delivered.)