title: creating orderer genesis block without cryptogen
body: <p>I am currently trying to build a production hyperledger-fabric setup. Therefore I am using a CA instead of cryptogen. 
  My structure looks like this:</p>
  
  <ul>
  <li>orderer</li>
  <li>org1
  
  <ul>
  <li>peer0.org1</li>
  <li>peer1.org1</li>
  </ul></li>
  <li>org2
  
  <ul>
  <li>peer0.org2</li>
  <li>peer1.org2</li>
  </ul></li>
  </ul>
  
  <p>and I have 2 CAs (1 for every org). 
  I have registered and enrolled orderer, peer0.org1, peer1.org1 and Org1Admin @CA1
  and peer0.org2, peer1.org2 and Org2Admin @CA2.
  The orderer has ROOT_CERTS of both CAs.</p>
  
  <p>But how can I create the orderer genesis block based of those MSPs?
  The configtx.yaml asks for an 'MSPDir' when describing the organizations, but I don't have an MSP directory for the organization itself, I only got the MSPs of the identites. Do I have to set up a specific folder structure for this? </p>