Improve documentation, fix passing loop_body by ref in forall_here_async
Improve documentation, fix passing loop_body by ref in forall_here_async

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