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
They are solved now so I removed them. There is one aspect though we should reconsider maybe. I noticed the full name of a file descriptor is composed of the package name + file name. This is a good convention to be followed by users but should probably not be enforced by us. I just noticed protoc does not require this.