INGInious now uses external docker registry to get the container images.
Merge branch 'master' of githubGuillaume:UCL-INGI/INGInious

Conflicts:
	containers/default/bin/INGInious
	containers/default/bin/archive
	containers/default/bin/feedback
	containers/default/bin/getinput
	containers/default/bin/parsetemplate
	containers/default/inginious/feedback.py
	containers/default/inginious/templateparser.py
	containers/default/inginious/tests.py
	containers/pythia0compat/pythia.py
	containers/pythia0compat/pythia_input.py
	containers/pythia1compat/INGInious
Fix error handling