rename NumberOfRetries to AllowedAttempts, default AllowedAttempts to 0

NumberOfRetries implies a separate first attempt
default AllowedAttempt to zero to make it's use explicit to help prevent bugs
add Loser message to validate ultimate fail behavior
fix bug registering latest subscribers

- instead of checking for hubtypes for latest subscribers, we were checking for subscribers for specific hub types, whether they were marked as IsLatest or not.