Change icons in the chronos templates to the new icon set

aleksis/apps/chronos/templates/chronos/all.html

...s/apps/chronos/templates/chronos/automatic_plan/list.html

...sis/apps/chronos/templates/chronos/edit_substitution.html

...s/apps/chronos/templates/chronos/partials/datepicker.html

.../apps/chronos/templates/chronos/partials/week_select.html

aleksis/apps/chronos/templates/chronos/substitutions.html

...s/apps/chronos/templates/chronos/substitutions_print.html

aleksis/apps/chronos/templates/chronos/timetable.html

aleksis/apps/chronos/templates/chronos/widget.html