closes #1134

branch 'nextcloud' of https://github.com/yeah/mailinabox

e.g. code comments and user-facing prompts/outputs which can be safely changed without risking to break anything

Since it says "RCMCardDAV requires at least PHP 5.6.18. Older versions might work", let's hope for the best.

Also hiding its preferences panel in settings since if it doesn't work, we don't want folks using it for anything but connecting to ownCloud contacts.

To comply with #1098 and avoid failed setups while testing with Vagrant

* Move variable assignment up and do not use call arguments directly

* Upgrade ownCloud to latest patch release 9.1.4

also move owncloud hash to its own variable

Added an alternative mail log scanning script for use from the command line (and monitoring, at a later stage)

merges #970

The `default_vsz_limit` is the maximum amount of virtual memory that can be allocated. It should be set *reasonably high* to avoid allocation issues with larger mailboxes. We're setting it to 1/3 of the total available memory (physical mem + swap) to be sure.

See here for discussion:
- https://www.dovecot.org/list/dovecot/2012-August/137569.html
- https://www.dovecot.org/list/dovecot/2011-December/132455.html

SSH fail2ban jail is not enabled by default and so the jail does not load.

in order to correlate with the management interface.

pip<6.1 + setuptools>=34 have a problem with packages that
try to update setuptools during installation, like cryptography.
See https://github.com/pypa/pip/issues/4253. The Ubuntu 14.04
package versions are pip 1.5.4 and setuptools 3.3. When we
install cryptography under those versions, it tries to update
setuptools to version 34, which became available about 10 days
ago, and then pip gets permanently broken with errors like
"ImportError: No module named 'packaging'".

The easiest work-around on systems that aren't already broken is
to upgrade pip and setuptools individually before we install any
package that tries to update setuptools.

Also try to detect a broken system and forcibly remove setuptools
first before trying to install/upgrade pip.

fixes #1080, fixes #1081, fixes #1086
see #1083
see https://discourse.mailinabox.email/t/error-with-pip-and-python/1880
see https://discourse.mailinabox.email/t/error-installing-mib/1875

move the custom exclusive process code from utils.py into a new python package named exclusiveprocess

* Added an error message to handle exceptions when the setup script is trying to determine the latest Miab version

* Fixed issue with relative path for rsync relative names

Actually using the parsed URL `path` part, instead of doing a lousy split().
Renamed the `p` variable into something more sensible (`target`).

Fixes: #1019

* Added more verbose error messages upon rsync failures

fixes #1033

* Added command to test file listing

fixes #834