[VERSION] Add app version in the help message

The version is obtained with the git describe command. With this solution the app version is based on the current git tag of the code; if the last commit is not associated with a tag, the hash of the commit is present in the app version: eg: 1.0-2-gb681d0f this means that the current app version is 2 commit ahead of tag 1.0 and the last commit hash is b681d0f