finished displaying vacation periods and holidays on internship modal
dialog
* adapted function getHolidaysAndVacationPeriods(...) so that it returns
 the same attributes for both types
* added function getDynblock(...) that creates the html for a dynamic
 vacation/holiday block
* adapted event handler 'edit-internship-button' so that it adds the
 dynblocks to the modal dialog
Merge branch 'master' of https://github.com/mb4/PE-Zeiterfassungstool