Add missing img alt-attributes
Add editor modal info section
Use static method when appropriate
Rename aktivitet-listing -> aktivitet_listing

The minus char isn't supported because when accessing widget context from
the editor template, the widget name is used ({{ widget_data.foo }}) and
the template language doesn't support the minus character.
Add method to get foreninger sorted with type data

Existing methods include only the type code, this will include their
human-readable name strings as well
Add editor controls for filtering on aktivitet organizer
Filter widget list on chosen organizer
Shorten down informational paragraph
Don't preselect in the DOM, will always be done by JS
Rehprase placeholder for required field
Add controls to filter on audiences
Implement filtering on audiences
Skip audience filtering if all choices are chosen
Add editor controls to filter on category
Implement filtering on category
Adjust widget modal header style
Hide filter controls by default
Factor out option iteration to util method
Rephrase text
Split long line