Expose logging levels on the command line

[StewBC]

I don't want to see any output from aloevera unless there's an issue. I was able to achieve this with the following changes to src/bin/aloevera.rs, line 80+81: stdout_log_level: Level::Warn, file_log_level: Level::Info,

Could the setting of these levels be exposed to the command line (or by default be set to Warn maybe)? I didn't see a None level (to supress file logging) but that's not really important.

BTW, you have written an enourmous amount of code here. It's all pretty cool and I appreciate the worlk you have done 👍