Tests check in flow and fixes bugs

See commits for changes.

Tested the following flows and fixed as necessary:

Check in item list on "Your QR Code page"
Check in with event ID as a participant
View check in item details as a participant
Create/edit check in items as an admin
Self-scan QR code to check in as a participant
Admin scan participant in to check in to an event without self check in enabled (both small and big QR code screens tested)
Check in updates leaderboard and check in item list points and checked status

Also fixed Android gradle issues to build APK since I needed to test QR code scanning on my Android - see slack for APK

ScottyLabs / tartanhacks_dashboard_v2