Add functionality to request GDPR information

[tomudding]

This makes board a separate role in the ACL to ensure that the board cannot access API users and GDPR exports.

The GDPR export functionality covers:

• [X] Activities
  • [X] Sign-ups
  • [X] Created
  • [X] Approved
• [X] Companies
  • [X] Companies approved
  • [X] Jobs approved
• [X] Decisions
  • [X] Decisions (from GEWISDB)
  • [X] GMM authorizations
  • [X] Member information (from GEWISDB)
• [X] Education
  • [X] Uploaded summaries
• [X] Frontpage
  • [X] Polls created
  • [X] Poll comments
  • [X] Poll votes
• [X] Photos
  • [X] Photographer
  • [X] Tags
  • [X] Votes
• [X] User
  • [X] Extra information (roles, login attempts, etc)

There is no UI for this (yet) as this is intended to be moved to the actual API in the future.

This closes GH-1773.