private ModifyableColumnFamilyDescriptor setValue(Bytes key, Bytes value) {
      if (value == null || value.getLength() == 0) {
        values.remove(key);
      } else {
        values.put(key, value);
      }
      return this;
    }
Constructor. Makes a deep copy of the supplied descriptor. TODO: make this private after the
HCD is removed.
@param desc The descriptor.
hbase-client/src/main/java/org/apache/hadoop/hbase/client/ColumnFamilyDescriptorBuilder.java