Fix a few misc things

[ddabble]

Proposed changes

Highlights:

• Added a link to the Django admin change form at the bottom of the form of "content boxes" that have extra change permissions (like the front page of the internal site) (994bfa612d5c9ea16a503143170926bb69d0263e)
  • This is only visible to users who have permission to modify those content boxes through Django admin
• Code cleanup (a0e50a5da5b1b9bfcef014ff281aea37f2f1ab08)

Other than that, see the other commits' messages.

Areas to review closely

None in particular.

Checklist

(If any of the points are not relevant, mark them as checked)

• [x] Created tests that fail without the changes, if relevant/possible
• [x] Made sure that your code conforms to the code style guides and that any common code smells have been addressed
  • (It's not intended that you read through this whole document, but that you get yourself an overview over its contents, and that you keep it in mind while taking a second look at your code before opening a pull request)
• [x] Added sufficient documentation - e.g. as docstrings or in the README, if suitable
• [x] Added your changes to the "Unreleased" section of the changelog - mainly the changes that are of particular interest to users and/or developers, if any
• [x] Added a "Deployment notes" section above, if anything out of the ordinary should be done when deploying these changes to the server

[codecov[bot]]

Codecov Report

Merging #636 (2826b57) into dev (9785d37) will increase coverage by 0.01%. The diff coverage is 93.75%.

@@            Coverage Diff             @@
##              dev     #636      +/-   ##
==========================================
+ Coverage   87.27%   87.28%   +0.01%     
==========================================
  Files         135      135              
  Lines        5672     5677       +5     
==========================================
+ Hits         4950     4955       +5     
  Misses        722      722              

Impacted Files	Coverage Δ
src/contentbox/tests/urls/urls_internal.py	100.00% <ø> (ø)
src/dataporten/social.py	52.94% <ø> (ø)
src/dataporten/views.py	74.19% <ø> (ø)
src/docs/urls.py	100.00% <ø> (ø)
src/faq/views.py	100.00% <ø> (ø)
src/groups/models.py	100.00% <ø> (ø)
src/internal/models.py	93.33% <ø> (ø)
src/internal/templatetags/member.py	89.18% <ø> (ø)
src/internal/urls.py	100.00% <ø> (ø)
src/internal/validators.py	85.71% <ø> (ø)
... and 20 more

[ddabble]

Merging without explicit approval from another member, as the Dev committee previously agreed to merge these changes and assume they're relatively bug-free, simply to get things done quicker.