Scheduling Logic: implemented first major structure

- added several classes to provide a appropriate architecture (course, customer preferences,
  personalized timetable,...)
- encapsulated Date/Time functions to utility class
- added Java Joda support for DateTime handling
- added some mockups to test user preferences and settings
- implemented first parts of time slot scheduler
- current features: application is able to add blocking-calendar entries
  and can detect free time slots from calendar data