Schema Version must be zero for 1.4 release

[ashcherbakov]

• A new schemaVersion field has been introduced in 1.4 release for all types and transactions (see https://github.com/zigbee-alliance/distributed-compliance-ledger/tree/master/proto/zigbeealliance/distributedcomplianceledger)
• Currently this field is optional but editable (see tx.proto) and exposed in CLI/UI.
• The default value (if the user doesn't set it) is Zero, as expected. However, a user may edit it to some non-zero value.
• We should not allow non-zero values of SchemaVersion in 1.4. On the other hand, we may need it to be editable in future.
• The easiest way to do it is to add a (static) validation to all commands (in all tx.proto) so that is the input SchemaVersion != 0, the command is rejected.

Recommended Steps:

1. Add validation for a schemaVersion field to all Create/Update commands in all tx.proto files (https://github.com/zigbee-alliance/distributed-compliance-ledger/tree/master/proto/zigbeealliance/distributedcomplianceledger)
   • Easiest way: "validate:\"gte=0,lte=0\""];
   • Consider more elegant ways to check equality using https://github.com/go-playground/validator/blob/master/README.md#comparisons (eq). Needs to be supported in https://github.com/zigbee-alliance/distributed-compliance-ledger/blob/master/utils/validator/validator.go.
2. Re-generate code from .proto files
   • https://github.com/zigbee-alliance/distributed-compliance-ledger/blob/master/scripts/README.md
3. Add unit tests for all affected types/messages
   • https://github.com/zigbee-alliance/distributed-compliance-ledger/blob/master/x/model/types/messages_model_test.go and similar tests for all modules/types
4. Fix other tests if needed (CI must pass)
5. Update documentation to point out that schemaVersion field can not be non-zero for 1.4 release in https://github.com/zigbee-alliance/distributed-compliance-ledger/blob/master/docs/transactions.md