revised intros and added content.pod

As suggested some time ago, I thought it would be useful to
a) unify the beginning of all the Synopses. Since various synopses use different start material headers, such as 
<no header>
"Overview"
"Introduction"

I added a new =head1 Document Description

b) Most Synopses have no Apocalypse ancestor, whilst where there is an ancestor, it is long long gone.

So I suggest rewriting to eliminate the history from all the Synopses, but the first.

c) I have rewritten the start of Synopsis 1

d) All these changes allow for a new contents.pod to be generated. A script to do this is included in this repo. Contents.pod is more a proof of concept file.

Apart from Synopsis 1, the revision have been relatively minor.