Add Debug to make compatible with log4rs

[avn-tnl]

Add an implementation for Debug to make EventLog compatible with Append of log4rs: https://docs.rs/log4rs/latest/log4rs/append/trait.Append.html#impl-Append-for-T
This would allow for EventLog to be used just like the other appenders in log4rs.

[bbqsrc]

@avn-tnl is there a reason for not just returning the inner level directly, or using .debug_tuple ?

[avn-tnl]

@bbqsrc I was not introduced to debug_tuple yet, so sorry about that. I think the type of logger and level is about all the debug information a consumer of the library would want, but I am open to suggestions.