hash-existing-files list all the files used for hash that are not
handled by buildout. For those files, the hash is calculated as soon as
the __init__ function so that if there is a change in those files,
buildout will remove the existing wrapper (it will uninstall the
section) and replace it with the new wrapper.

Use xz instead of gzip.
Also put the cron script in etc/service instead of etc/run (to have the
"cron-on-watch" process)

This is a follow-up of commit 5c980caf,
now that the new code of the 'wrapper' recipe is used (1.0.58 released).

  This change allow us simplify accross the instances usage of logrotate

When a process is stopped:
- it may not have emitted logs since previous rotation: add "missingok"
  As a direct consequence: stop using logrotate recipe.
- its pid file (if applicable) may be missing: test its non-empty presence
  before calling slapos-kill
Also, stop using slapos.cookbook:logrotate.
Update obvious users (cloudooo, neoppod, erp5, monitor, re6stnet).

- logrotate: make stack with cfg.in containing sections for logrotating with dcron and gzip
- neoppod: use this logrotate stack

Before it was only possible to make an ERP5 cluster connect to a NEO cluster
that was instanciated separately, by passing "name" and "master_nodes"
connection parameters in "storage-dict".

For an internal NEO DB, "name" and "master_nodes" is filled automatically
and you must instead pass a "server" dict, with same parameters as in NEO SR.
Currently, a NEO cluster name must be given. Later, we hope to generate a good
name automatically.

All this was implemented by refactoring NEO & ERP5 SR, with common files.
For the ERP5 SR, the root partition also serves as "root" partition for NEO
partitions: in other words, there's no second empty partition.

This work has nothing to do in erp5-component branch, and is preventing it
from being merged to erp5 banch more often.
Conflicts because of non-reverted
6d1a9805 have been resolved to that its
intent is preserved with non-cluster ERP5 SR.

This reverts commit 77976a14.
This reverts commit 7aa1d92c.
This reverts commit 80062015.
This reverts commit 36ed58f2.
This reverts commit 1fe3f466.
This reverts commit 7731726a.
This reverts commit eb2016c4.