Working saving of submission
auto assessment, ref to whitelist token -> id, progress bar update over sockets

Replace answer.correctness with an auto assessment using a pre save hook on answer.
Replaced the whitelist refrences from tokens to  ids.
Added the progress bar logic over socket for the new progress bar.
Small bug fixes
Merge branch 'peer-to-peer' of github.com:ASQ-USI/ASQ into peer-to-peer
Whitelist: uid -> user & fixing tests
Cleaning tests