teacher/student panel: display different colors for each lab depending on score per lab

[meling]

For each lab, we could display different colors depending on how many points a student/group has gotten. For example:

• White (0%)
• Blue (0%-59%, no slip days used)
• Yellow (0%-59%, < 5 slip days used)
• Red (0%-59%, > 5 slip days used)
• Green (60%-100%)
• Red?? (> 5 slip days):
• Black (> 10 slip days)

We should have a parameter for number of slip days (X) and the pass level (Y=60%) which should be configurable in the settings panel.