Feature/admin workflow surveys page

• Adds status fields to surveys and responses
• Creates a survey admin page, on which you can set the survey status and create a new survey (url /survey/admin/surveys)
• Slightly different way of opening the survey in the frontend, both the year and nren are url params now
• Add a migration to add the 2022 survey model to the database; dont read it from file anymore
• Adds a dump_survey_json command to assist with making edits to the survey model
• Fixes some small bugs in the conversion mapping
• Use the built-in surveyjs templating for the years and use a better way of validating urls
• Fix a bug that made the validation of the sum of percentages crash on 0.x numbers

Note that all existing surveys and responses are removed by one of the migrations. After running the migrations you will have to run conversion