Options page

• Rename menu entry to "Options"
• Granularity of points (0.25; 0.5; 1 shall be possible) (previous #80 (closed) ) shall also be settable in this Options menu and not only in the start window
• Grade boundaries table (previous #87 (closed)) needs improvement for Min/Max label and show all limits, also for 5.0
• Setting to adjust, if points in the point histogram shall be grouped for better visibility. Default: 1 point groups
• Split exam: Checkbox if both exams have to be passed individually, see #87 (closed) (default: false)