This supports stestr unit tests as well linting with pep8 / flake8

This uses pbr for setup.py which automatically extracts features
and entrypoints out of setup.cfg otherwise you would have to type
this by hand.

Some fields of setup.cfg still need changing the have been
commented out in the meantime.

L2SS-251: SKA Tango images moved

Closes L2SS-251

See merge request !54

Any images missing from the artefact.skatelescope.org registry are now
configured to be downloaded from git.astron.nl:5000

This patch ensures all images available from artefact.skatelescope.org
are pinned to a specific version. This is necessary as :latest is not
available on this registry.

L2SS-251: Refer to the DOCKER_REGISTRY environment variables in .env for source images, instead of hard-coding them in the Dockerfiles

L2SS-199: Remove asyncua requirement as it's unused. Upgrade opcua lib requirement to 0.98.13.

Closes L2SS-199

See merge request !52

Resolve L2SS-230 "Add sdp sim"

Closes L2SS-230

See merge request !48

Resolve L2SS-246 "Capitalise sdp"

Closes L2SS-246

See merge request !51

L2SS-232: Add a Docker tag/push script for local images

Closes L2SS-232

See merge request !49

L2SS-225:  Fix rebuild_system_from_scratch.sh to also function on CentOS7

Closes L2SS-225

See merge request !41

L2SS-229 "Add gitpython and python-logstash-async to itango"

Closes L2SS-229

See merge request !46

L2SS-231: add a device with 20 attributes that generate random numnbers on read

Closes L2SS-231

See merge request !47

L2SS-192: Provide interface for raw header fields, add example packet (needs...

Closes L2SS-192

See merge request !45

L2SS-192: reserved_0 -> reserved to not be overly defensive. if there are multiple reserved fields in the future, we'll deal with that by then.

L2SS-228: Fix mount path for the host's tango repo dir to /opt/lofar2.0/tango/

Closes L2SS-228

See merge request !44