added middleware to redirect the user to a confirmation page whenever a study has a privacy_notice assigned, this is enforced and the user haven't accepted yet. superusers excluded

Merge branch '329-privacy-notice' of ssh://git-r3lab-server.uni.lu:8022/NCER-PD/scheduling-system into 329-privacy-notice

WIP: first draft of privacy notice, go to /privacy_notices to list them and add them, please, create the folder privacy_notices/ before running

Resolve "configurable study fields"

Closes #339

See merge request NCER-PD/scheduling-system!265

Resolve "clean configuration"

Closes #343

See merge request NCER-PD/scheduling-system!271

Resolve "fix datetime without TZ warnings"

Closes #360

See merge request NCER-PD/scheduling-system!272

Resolve "branding"

Closes #357

See merge request NCER-PD/scheduling-system!273

Resolve "should we remove __unicode__ method?"

Closes #356

See merge request NCER-PD/scheduling-system!274