Allow setting DS records in create_domain and update_domain

The DS records consist of 4 values:
- keyTag: unsigned short (2 bytes)
- alg: unsigned byte
- digestType: unsigned byte
- digest: binary hex

NOTE: the current CL doesn't support keyData, neither as the optional field in dsData nor as a replacement for dsData

The command tool accepts DS records as a string, where the 4 values are given
as one string separated by white-spaces as follows:
<keyTag> <alg>  <digestType>  <digest>

e.g. something like:
60485 5  2  D4B7D520E7BB5F0F67674A0CCEB1E3E0614B93C4F9E99B8383F6A1E4469DA50A

which is how it's written in Zone files, allowing easy copy-paste from existing values.
ommas is confusing when using spaces.

The various "numbers" (keyTag, alg, digestType) are only checked that they are
positive integers - the rest is left for the server.

digest it checked to be an even-lengthed hex string.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=184583068

java/google/registry/tools/CreateDomainCommand.java

@@ -59,7 +59,8 @@ final class CreateDomainCommand extends CreateOrUpdateDomainCommand {
               "registrant", registrant,
               "admins", admins,
               "techs", techs,
-              "password", password));
+              "password", password,
+              "dsRecords", DsRecord.convertToSoy(dsRecords)));
     }
   }
 }