Merge pull request #27 from FraGoTe/stage

Change of message when there is a PLEX exam - refs BT#7729
Merge pull request #28 from FraGoTe/stage

Avoid incomplete exercises - refs BT#7729
Merge pull request #29 from FraGoTe/stage

If there is an exam incomplete let the user continue taking the PLEX - refs BT#7729