Ideas:

• (tick) add arbitrary number of columns (columns of diff types - boolean, number, string)
• totals
• Let users delete their entry
• ADG all the things

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• csv compatible
• Let users edit entry
• Fix sorting
• Do something about the attend button.
• mandatory fields
• Mobile compatible
• new column types (limited values)
• Sort by click on field
• ical export
• Fix print
• Fix tests