added period support to the Items database; added ability to select a period when adding an item; filter items on the period fragments to only show items from that fragment; see #23
commented out line that empties database
Added Settings activity and spinners
Fixed all items being added fragment when all items deleted
Message if no items in a period added, also removed some extra code
Added message string and removed unneccesary layout params code
Added Edit period on edit screen
Added string of error message for no period selected in edit activity
implemented selecting only timestamps in the current period (#25)