Combining multiple logs

Prerequisites: install abstractions module.
Multiple ILog instances can be combined with CompositeLog:
var consoleLog = new ConsoleLog();
var fileLog = new FileLog(new FileLogSettings());
var combinedLog = new CompositeLog(consoleLog, fileLog);
CompositeLog forwards incoming log events to all underlying logs.
Its IsEnabled(LogEvent) method returns true if any of the underlying logs is enabled for given event.
Its ForContext(string) method invokes ForContext on all underlying logs and returns a new CompositeLog based on the results.