import public not supported in TypeScript code generator

It looks like `import public` feature of Protofile is not supported correctly when generating TypeScript code.

The generated code contains plain `import * as ` in the file that corresponds to the Protofile with `import public`, and so the file where the _transitive_ type is used is invalid, because of missing import. As TypeScript doesn't support a feature like `import public` (IMHO), the code generator should generate the _transitive_ imports _manually_.