split jail role into two

* base-jailhost ensures that the service host has necessary
  infrastructure installed and configured (ezjail)
* jail role is to be used to create jails on the jail host
* remove ezjail.flavour file (we do not use it at the moment)
* do not enable 'jail' service, enable 'ezjail' instead
* use 'ftp.freebsd.org' (for some reason I had problems with
  freebsd.isc.org)
* do not install lib32 stuff in ports tree
* introduce a number of base-jailhost variables to avoid typing errors
unify bootstrapping of jails and service hosts

* create a template for the script to perform actual bootstrapping
* create a playbook to bootstrap service hosts
* make use of the playbook in 'bootstrap' script
* add bootstrapping of jails upon creation
add a todo list
configure jails
configure www.buildbot.net