Also:
- reinstall the pre-commit hook
- fix the minor pep violations

Created from the previous steps:
```
python3 -m manage dbshell
> insert into dbversion(version, description) values (1, 'Work in
Progress');
> insert into client(name) values ('hal');
> exit
python3 -m manage dumpdata --format=yaml > test.yaml
rm test.yaml
python3 -m manage loaddata data_deposit
```

```
python3 -m manage makemigrations
```

- Use default time for dbversion release field
- deposit.complete_date can be null (it's updated when the deposit is
  deemed complete, in the mean time, it's null)

```
python3 -m manage makemigrations
python3 -m manage sqlmigrate deposit 0001
python3 -m manage migrate
```

```
python3 -m manage startapp deposit
```

```
cd swh-deposit
django-admin startproject swh
```

Summary:
Context: SWH, Inria and the CCSD (in charge of the HAL's archive) are working on pushing
HAL's source code deposit into SWH with SWORD protocol.

This specs were edited by ardumont and myself on the notepad
available on: https://pad.riseup.net/p/t4mJsj9RB0OQ

Reviewers: ardumont

Differential Revision: https://forge.softwareheritage.org/D220

Summary:
Context: SWH, Inria and the CCSD (in charge of the HAL's archive) are working on pushing
HAL's source code deposit into SWH with SWORD protocol.

This specs were edited by ardumont and myself on the notepad
available on: https://pad.riseup.net/p/t4mJsj9RB0OQ

Reviewers: ardumont

Differential Revision: https://forge.softwareheritage.org/D218

note: deleted docs/specs.md to remove redundancy

Related T718

Also remove unused dependencies

This permits to share state (e.g configuration) between those
endpoints.