lazy-timesheet

1. Holiday hours and holiday days were fixed by using sp.ceil and
   sp.floor instead of normal rounding. It has the right results now.
2. Under advanced settings one can now exclude a list of specific dates
   from being used as workingdays. Those dates are excluded just like
   public holidays or Sundays.
3. Under advanced settings one can now provide a list of specific dates
   with preset workinghours. Might be useful if one has specific dates
   that must not exceed a certain duration of working.

TODO: Make everything new and better and GUI and pandas.