Assign 2 (or more?) iTags per perticipant

[zingo]

During 2nd race test one participant managed to turn off the iTag by misstake having two tags per person could fix this.
This would also make "fast" runners that don't stop more likely to be detected.

• This will need to chanage the database from tag->participants to participant->tags[]
• The gui should show the dual tag in some way
• Nice to have: You need to be able to add & assign/change tags to users in the GUI (could also be hardcoded too always use two tags per user)

[zingo]

Initial version with 39ba7c0