code: public boolean cacheEnabled() {
          if (this == EMPTY_CONF) return false;
          if (null == _cacheEnabled) {
              Boolean ce = get(CACHE_ENABLED);
              if (!ce) {
                  _cacheEnabled = false;
              } else {
                  if (engine.isProdMode()) {
                      _cacheEnabled = true;
                  } else {
                      Boolean po = get(CACHE_PROD_ONLY_ENABLED);
                      _cacheEnabled = !po;
                  }
              }
          }
          return _cacheEnabled;
      }
docs: Return true if cache is not disabled for the engine instance. A cache is disabled when
  <ul>
  <li>{@link RythmConfigurationKey#CACHE_ENABLED} is <code>true</code> or</li>
  <li>{@link RythmConfigurationKey#CACHE_PROD_ONLY_ENABLED} is <code>true</code> and
  {@link RythmConfigurationKey#ENGINE_MODE} is {@link org.rythmengine.Rythm.Mode#dev}</li>
  </ul>
  
  @return true if cache enabled