ISPN-4758 Protobuf schema parser should not allow duplicate type definitions

Jira: https://issues.jboss.org/browse/ISPN-4758
 https://issues.jboss.org/browse/ISPN-4761
https://issues.jboss.org/browse/ISPN-4765
Can we remove those comments or maybe create JIRAs for the ones not yet fixed?