feat: add DataObjectGroup on all [Binary|Physical]DataObject descendents of DataObjectPackage.

Use <rng:zeroOrMore/rng:choice> grouping all [Binary|Physical]DataObjects to avoid the problem
if [Binary|Physical]DataObject order (closes #35)

--HG--
branch : seda21
5 jobs for topic/seda21/zero in 1 minute and 11 seconds (queued for 4 seconds)
Status Name Job ID Coverage
  Lint
passed check-manifest #458715
lint check-manifest

00:00:24

failed flake8 #458714
lint flake8

00:01:11

passed yamllint #458716
lint yamllint

00:00:53

 
  Tests
skipped py3 #458717
tests py3
 
  Build Debian Package
skipped build-debian #458718
debian manual
 
Name Stage Failure
failed
flake8 Lint
ERROR: InvocationError for command /builds/cubicweb/cubes/seda/.tox/flake8/bin/flake8 . (exited with code 1)
___________________________________ summary ____________________________________
ERROR: flake8: commands failed
Uploading artifacts for failed job
Uploading artifacts...
gl-code-quality-report.json: found 1 matching files and directories

Uploading artifacts as "codequality" to coordinator... ok
id=458714 responseStatus=201 Created token=EAWtzxpg
Cleaning up file based variables
ERROR: Job failed: command terminated with exit code 1