public void setConfiguration(String key, String value) {
    if (value == null) {
      removeConfiguration(key);
    } else {
      configuration.put(key, value);
    }
  }
Setter for storing a configuration setting in {@link #configuration} map.
@param key   Config key. Same as XML config key e.g. hbase.something.or.other.
@param value String value. If null, removes the setting.
hbase-common/src/main/java/org/apache/hadoop/hbase/NamespaceDescriptor.java