[FAB-1994] - support intermediate CAs in MSP

MSPs should support intermediate CAs to permit validation of certificate
chains longer than 2. This change set adds the relevant field to the msp
config protobuf.

Change-Id: Ia521091803e9c93536bcd5f4a0e4ca780b44a5b9
Signed-off-by: Alessandro Sorniotti <ale.linux@sopit.net>

protos/msp/mspconfig.proto

@@ -48,19 +48,31 @@ message FabricMSPConfig {
     // this can refer to the Subject OU field or the Issuer OU field.
     string Name = 1;
 
-    // List of root certificates associated
+    // List of root certificates trusted by this MSP
+    // they are used upon certificate validation (see
+    // comment for IntermediateCerts below)
     repeated bytes RootCerts = 2;
 
+    // List of intermediate certificates trusted by this MSP;
+    // they are used upon certificate validation as follows:
+    // validation attempts to build a path from the certificate
+    // to be validated (which is at one end of the path) and
+    // one of the certs in the RootCerts field (which is at
+    // the other end of the path). If the path is longer than
+    // 2, certificates in the middle are searched within the
+    // IntermediateCerts pool
+    repeated bytes IntermediateCerts = 3;
+
     // Identity denoting the administrator of this MSP
-    repeated bytes Admins = 3;
+    repeated bytes Admins = 4;
 
     // Identity revocation list
-    repeated bytes RevocationList = 4;
+    repeated bytes RevocationList = 5;
 
     // SigningIdentity holds information on the signing identity
     // this peer is to use, and which is to be imported by the
     // MSP defined before
-    SigningIdentityInfo SigningIdentity = 5;
+    SigningIdentityInfo SigningIdentity = 6;
 }
 
 // SigningIdentityInfo represents the configuration information