Installer flows

[Rod Widdowson]

Whilst I am making progress on most fronts, I've been thrashing slightly
trying to work out how we need to behave in the face of various install and
upgrade situations.

I came up with this
https://wiki.shibboleth.net/confluence/display/~rdw@iay.org.uk/InstallerFlow
s  Some of it is windows specific, a lot isn't (particularly the behaviour
for new installation).

Comments (particularly on my slightly cavalier approach to relying-party in
aV2->V3 update) are, as always, welcome.

R