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/maintainable-date-range' into mrmcd-2014
Configure application for MRMCD 2014.
Colorize ActionBar for MRMCD 2014 (Draft).
Customize conference URL for MRMCD 2014.
Configure color for tracks for MRMCD 2014.
Turn ActionBar into red for MRMCD 2014.
Turn background into red for MRMCD 2014.
Customize launcher icon for MRMCD 2014.
Customize action bar icon for MRMCD 2014.
Customize about dialog image for MRMCD 2014.
Customize notification icon for MRMCD 2014.
Customize spinner for MRMCD 2014.

+ The spinner is used for day selection.
Customize checkboxes for MRMCD 2014.
Configure link for Google PlayStore for MRMCD 2014.
Remove copyright notice for 30C3 artwork for MRMCD 2014.
Add disclaimer to info dialog for MRMCD 2014.
Update link to repository for MRMCD 2014.
Change feedback URL for MRMCD 2014 (not tested yet).