dakweb: /sha256sum_in_archive/<sha256sum> endpoint

See merge request ftp-team/dak!76

This patch creates a new /sha256sum_in_archive/<sha256sum>
endpoint in dakweb. The endpoint allows for searching for
files with a marching sha256sum in the archive.

I have also taken the time to fix docstrings of file_in_archive
which wrongly indicated that the return type was a dictionary.

There is no need to create empty files for source-only uploads.

The problem from c51e71bb occured
again with a call to `ssh` in a different place.  This should make
sure we don't run into this problem again...

Fix dinstall stage file

See merge request ftp-team/dak!70

update needed packages

See merge request ftp-team/dak!75

queued uses Perl modules instead of `md5sum` and `mkfifo`.

queued doesn't inspect uploaded files, so `tar`, `gzip` and `ar`
as a poor man's dpkg are not needed either.

add current crontab from seger

See merge request ftp-team/dak!73

the name of the script has been changed

See merge request ftp-team/dak!74

Fix E231: Missing whitespace after ',', ';', or ':'

See merge request ftp-team/dak!72

Fix E704: Multiple statements on one line (def)

See merge request ftp-team/dak!71

use hashlib instead of deprecated md5 module

See merge request ftp-team/dak!69

Fix E115: Expected an indented block (comment)

See merge request ftp-team/dak!63

Fix E502: The backslash is redundant between brackets

See merge request ftp-team/dak!64

Fix E272: Multiple spaces before keyword

See merge request ftp-team/dak!65

Improve run dbtests

See merge request ftp-team/dak!68

Signed-off-by: NNiels Thykier <niels@thykier.net>