Non-generic logger name for better filtering

Fixes #32.

The `ILog` used by `Command` is just a single logger for all possible Commands, which makes any log filtering to hide/show logs for specific commands difficult.

This changes the log name to incorporate the command's name into it.

*Old*
> 2014-11-30 00:00:49,075 hostname [INFO ] [Hudl.Mjolnir.Command.Command`1] InvokeAsync Command=group-name.CommandName Breaker=breaker-name Pool=pool-name Timeout=15000

*New*
> 2014-11-30 00:00:49,075 hostname [INFO ] [Hudl.Mjolnir.Command.group-name.CommandName] InvokeAsync Command=group-name.CommandName Breaker=breaker-name Pool=pool-name Timeout=15000