Let parsing fail when XML is invalid.

+ Check for missing 'end' attribute in 'day' element.
+ Avoid running DateFieldValidation when parsing already failed since
  an exception thrown by this class causes an application crash.
  Instead show a meaningful Toast message.
Increase maintainability for date range assignment.
Merge branch 'feature/check-for-missing-xml-attribute' into froscon-2014
Fix minor offset in time range used by the alarm manager.

+ Merge branch 'feature/maintainable-date-range' into froscon-2014.
Bump application version to v.1.29.6 (FrOSCon Edition).