Write a file `uuid` in server's data directory that contains random UUID, generated at startup if file does not exist.

It will be used for several purposes:
- to anonymously identify server in Sentry (currently Sentry is unusable);
- (possible future usage) to identify server in ensemble.

@tavplubix comments?
{
    BaseDaemon::initialize(self);
    logger().information("starting up");
    LOG_INFO(&logger(), "OS name: {}, version: {}, architecture: {}",
        Poco::Environment::osName(),
        Poco::Environment::osVersion(),
        Poco::Environment::osArchitecture());
}
std::string Server::getDefaultCorePath() const
{
    return getCanonicalPath(config().getString("path", DBMS_DEFAULT_PATH)) + "cores";
}
void Server::defineOptions(Poco::Util::OptionSet & options)
{
    options.addOption(
        Poco::Util::Option("help", "h", "show help and exit")
            .required(false)
            .repeatable(false)
            .binding("help"));
    options.addOption(
        Poco::Util::Option("version", "V", "show version and exit")
            .required(false)
            .repeatable(false)
            .binding("version"));
    BaseDaemon::defineOptions(options);
}
void checkForUsersNotInMainConfig(