start.sh stop.sh: check for privileges moved back to neubot/M-Lab
Do most of the reinstall/install work in initialize.sh

This commit modifies deploy.sh and initialize.sh to do most
of the work in the latter script.

When initialize.sh is invoked, it stops and clears the
previous neubot instance (if any); then, it installs,
starts and checks the new instance.
Revert "Update documentation: initialize.sh cannot invoke uninstall.sh"

This reverts commit 073fb27279... because it turns out I was
wrong: it is possible, in fact, to do most of the work from
the initialize.sh script.