New features.

TextFile now flushes its texts (every 3 seconds by default).
ApplyConfiguration can now block, waiting for configuration application.
GrandOutput exposes ExternalLog() methods that uses MonitorId Guid.Empty to emit contextless logs.
GrandOutput.Default now listens to ActivityMonitor.CriticalErrors and ExternalLog them. Other GrandOutput instances (than the Default one) can also track critical errors by setting HandleCriticalErrors property to true.