Allow filtering by availability in the pizza product admin

See merge request thalia/concrexit!753

Resolve "Adding/changing Thabloids: field "year""

Closes #598

See merge request thalia/concrexit!743

Resolve "Multilingual push notifications"

Closes #536

See merge request !736

Improve photos services code

See merge request !733

Update to Django 2.0.3

See merge request !740

Fix photos api title field

See merge request !737

Add TokenMiddleware

See merge request !738

Only set up templatecheck if installed

See merge request !734

Resolve "Add filtering to push notifications"

Closes #538

See merge request !665

revamed the categories to a model and added fields to device and message. Added filtering for pushnotifications

Run sphinx-build on all cores

See merge request !731

Use Orientation EXIF tag in photo to determine orientation on upload

Closes #591

See merge request !730

Fix RegistrationInformationfield ordering

Closes #592

See merge request !732

Closes #592

Use `sphinx-build -j` and `nproc` to distribute collecting and compiling
the documentation over all cores.

Improve docs for the announcements module

Closes #588

See merge request !724

Clean up and document utils package

Closes #587

See merge request !726

Fix other test warnings

See merge request !728

Suppress unclosed file handle warnings

Closes #589

See merge request !727

Fix event registration saved Dutch message

See merge request !729

One about timezones, the other about a deprecationwarning

Further improve documentation

Include docs for utils submodules

docs build needs the dev requirements as it will import commands

Further improve docs

Delete unused ci-requirements.txt

Closes #571

See merge request !725

Improve docs for the merchandise site

See merge request !723