Fixing TaskStackTest for consistent sytnax in unit tests,
Improving comments in site class.
Removing system classes that were not differentiated from Posix.
Renaming the constructor to conf because siteIInfo no longer differs, setting an array key in the constructor so that isset() on the Site object won't break things.
Adding a configuration.ephemeral to specify configuration keys that are specific to a single run of drush fetcher and that should not be persisted to the site_info.yml file.