Add grid_submit utility

Utility to submit arbitrary scripts to the GRID.
Takes care of interaction with ALIEN and provides some
logging/monitoring and control framework.

For instance, the following command

```
./grid_submit.sh --ttl 40000 --script job_test.sh --topworkdir foo --label bar --jobname baz  \
                 --o2tag nightly-20210125-1                                                   \
                 --mattermost https://mattermost.web.cern.ch/hooks/HOOKID
```

submits the script 'job_test.sh' to the GRID with a TTL of 40000, to be stored
in top-level folder 'foo' (relative to the users home), having 'baz' as process name in ALIEN,
carrying production label 'bar', using the nightly software release 'nightly-20210125-1', and
sending progress information to an **optional** mattermost webhook

Author: sawenzel