Events module: modes, speakers and agendas

The event form grew up.

• Event type, mode (offline, online or hybrid, with a join link) and frequency (one-time or recurring)
• Mandatory city, state and country, plus tags and capacity
• Dynamic category and subcategory, and tick-boxes to list the event under other categories too
• Repeatable speakers with name, photo and bio
• A repeatable agenda with session, stage or room, speaker and times
• Free and paid tickets with ticket tiers as before