Latest updates from fmidue

• makes !92 (closed) obsolete (incorporates everthing of !92 (closed)), namely:
  • always use ByteString for IO on file system (close #849 (closed))
    • destructive, iff server is not configured to use UTF8 as file encoding
  • use actual used points when calculating points shown to students (in achieved .. of)
  • enhance providing feedback in frontend (enable changing Report, use current submission according to task setting)
  • always update best submission if it is better than the previous one
    • destructive, iff currently active exercises or old exercises are reactivated after update
  • use proper join in order to gain information on "Resultate" routes
  • some minor task updates
  • we had to perform most of the above changes as errors arose on ours or the students side during lectures
• additionally:
  • render multilang using text (#855 (closed))
  • fixes and improvements to commentary feature
  • add docker build script (e.g. for deployment)
  • several task upgrades
  • reenable fmidue tasks
  • enable configuring timeouts for backend server interactions
• close #849 (closed), #855 (closed), !92 (closed)

edited