`files.h/files.cpp`:
* Add end and else comments to all macros.
* Add "remove_all_inside" function which empties a directory without actually deleting the directory. This is necessary to handle the case where the directory is actually a directory symlink.
* Change remove_all to use std::remove when VCPKG_USE_STD_FILESYSTEM is set; this will engage POSIX delete support available on current Win10.
`commands.ci.cpp`: empty "installed".
`*/initialize_environment.*`: No longer clean the directories outside the tool.
`ci-step.ps1`: Remove unused console output tee-ing.
