Add boolean field for approving info sections before copying to next years event

[0xUnicorn]

A boolean field should be added for either InfoCategory or InfoItem so team leads can approve their info sections for marking them as ready for being copied to next years event

• Add boolfield is_approved for InfoItem.
• Add is_approved to form views for creating/updating InfoItem
• Show is_approved as an icon in the teams > info-categories list.
• Create BulkUpdateView using a formset for making checkboxes and a Mark all approved button in the teams > info-categories list.
• Show a warning alert to team lead when InfoItems isn't approved.