Complete the previous patch to schedules + small fixes

[PhilZ-cwm6]

• translation fr:
  • shorten some messages to fit the screen if needed because the max allowed error lines is 3 (Fr/eng)
• remove now unused messages
• do not show the schedule button when schedule list is empty + ensure NPE handling
• add missing space between Edit Schedule title and Schedule name in the EditSchedule dialog
• translate the new created schedule name
• if all auto-generated schedule names exist (>1000), do not rely on xml layout text field but on the translated new name message: this avoids a NPE if the layout text is removed in some code maintenance
• never modify the edited schedule name even if it is empty: do not change the schedule and throw an error message so user can rename it
• if an edited schedule has a null name (settings file corruption), notify the error
• add a few NPE checks also when renaming sync tasks and schedules