Add generator choice flags for SoftXMT BFS.
Add generator choice flags for SoftXMT BFS.

alexfrolov/grappa,uwsampa/grappa,alexfrolov/grappa,alexfrolov/grappa,uwsampa/grappa,buaasun/grappa,buaasun/grappa,alexfrolov/grappa,uwsampa/grappa,uwsampa/grappa,uwsampa/grappa,buaasun/grappa,buaasun/grappa,buaasun/grappa,buaasun/grappa,alexfrolov/grappa,alexfrolov/grappa,buaasun/grappa,uwsampa/grappa,alexfrolov/grappa,uwsampa/grappa