Framework: DataRequest implementation

More to add before merging:
- [x] Http handlers
- [x] TestFrameworkDataRequest
  - [x] reached ServeAsX
  - [x] id, req, data is correct
- [x] Close go routines at the end of lifecycle (Note: http server isn't closed. We need graceful shutdown solution.)
  - [x] close go routine
I don't know the semantic of http.Serve, but try to interpret Xiang's comment
it might make better to add a new member data in framework:
f.handler = newDataReqHandler(f)
and 
http.Serve(f.ln, f.handler)
will reuse the same handler object over and over.