This PR fixes the logging issue on Linux where logging is initialized before `-settingsFile` is parsed causing custom log settings to be ignored. (see ConsoleHost.cs and ManagedEntrance.cs)
The PR also includes basic logging tests for Linux and MacOS. PSSyslog.psm1 contains the functions to retrieve selected logged items (based on PowerShell's log id and a timestamp) and Logging.Tests.ps1 contains tests for Linux and MacOS.
