Excluded unused classes.
Copy-paste typo.
Comment typo.
More test cases.
Rotation subconfig in file sink config can now be initialized through constructor.
Rotator template can now be specialized by watcher type.

Watcher determines when it’s time to rotate. Basically it can be one or both of two types: size-based watcher and datetime-based.
As a result, all rotation-specific template template class and function signatures are replaced by simple fully-defined template parameter.