Changed some (many) comments + Finished MoreDialog

main.cpp --> Invalid import removed
aboutdialog.cpp --> added comment
addtaskdialog .cpp/.h --> changed some comments for documentation
moredialog .cpp/.h --> changed Labels into CheckBoxes and enabled to
"uncheck" (delete) relations with other tasks
relations.h --> don't remember, maybe just changed a comment
taskwidget.cpp --> changed creation of the MoreDialog instance (added
parameters)