update VERSION_DATE v1.6.1

simplify code

fix #834: creation of related subtask tickets

fix #833: creation of related defect tickets

Added tag v1.6.0 for changeset df78451a6d41

release version 1.6.0 v1.6.0

fix missing color adaption for headings on about page - relates to #730

(0) -300 -100 -30 -10 -7 tip

mercurial