add strings and layout for CrimeListFragment
create empty menu with add option
notify changes in start activity for result

instead of in onResume()
create menu with add Crime option
set layout empty crime list
Merge branch 'ch16_action_bar'
minor changes
make Crime class capable of JSON serialization
add save method to serializer
add saving of crimes to crime fragment
add loading of crimes from file
Merge branch 'ch17_files'