New feature: Keeping record of the latest release of each version with 'latest_version_tracking()' function
- A symlink 'latest' is created or updated for pointing the dir of the latest release.
- A file 'version' is created or updated for recording the version number of the latest release
- The file and the symlink are stored in each directory of the major version
- The function runs either after checking the existence of a release, or after downloading a new release.