Course Timetabling Solver: Optimization

Course Timetabling: Back-To-Back
- corrected conflict checking for a partially assigned back-to-back constraint when an unassigned class can have times with various lengths
  (e.g., MWF 3x50 and TTh 2x75)
  - previously only the lenght of the first available time was considered

Simple Search: max idle iterations during construction
- improved counting of idle unassignments of individual variables by marking the current counts when the solution is improved
- default limit on individual unassignments set to 1/10 of Search.MaxIdleIterations

Simple Search: progress
- show "Improving found solution ..." status during the HC/GD/SA phases even when a complete solution has not been found

Simple Search: Max Idle
- restore best solutio after the IFS phase if the best solution has more variables assigned than the current solution
- do not use construction/IFS neighbourhoods during the HC/SA/GD phases even when there are unassigned variables when max-idle is enabled
  - this is to avoid decreasing the number of assigned variables during the optimization phases