We noticed the subprocess that runs our 'cron' sometimes quits silently;
one possibility we see is that OOM kills it. In any case, we now also
check for the existence of the commands `sleep` or `timeout` in the
process table (`ps`) via the `livenessProbe`.

Address #60

Found two lines in robots.txt at UFAL's installation that seem ok. Add
also to our stash:
```
Disallow: /repository/*allzip$
Disallow: /repository/oai/requeststripped
```

Lately, we encountered hick-ups when the dspace container comes up but
the postgres container is still missing (although the containers will
restart until both start in the right order).

Here we add one `initContainers` that will poll the postgres db until
success.

Address #60

We use `timeout` from the coreutils package (should be part of many basic
installations - maybe with a different name) to force the individual
healthcheck commands too exit after a predefined timeout (300s); if this
doesn't help, send a SIGKILL.

This should help with the initial problem of hanging. A next step should
be to catch the `timeout` invoked exit and log this as an exceptional
happening.

Address #60

Instead of an external CronJob pod, or a supervisord cron daemon, we use
a subshell. Also we assume, the regular cronjob *also* needs to run when
the container starts. Insofar, we start the subshell, make sure it runs
a single time (and continues in the background) and then continue with
starting clarin-dspace.

Address #48

'502 Bad Gateway' errors from the k8s ingress server can be solved
(sometimes) by restarting the nginx pod. Here we check
https://clarin(-dev).eurac.edu:443

Addresses #53

- fixed some issues with Deployment Guide