throw an error if version is not semver

[pdmars]

Graviton assumes it can get the version by parsing the value passed to --sd-version, however, if a non-semver is passed then Graviton won't be able to determine the version. Graviton will still deploy a cluster, but it won't set the daemon flag and may result in systemd restarting Stardog continuously (e.g. when performing a SYNC_FULL).

Graviton should throw an error if a semver is not used.