Added gestures

Adds: Item activity now reacts to some gestures. Supported gestures are:
Single tap -> check/uncheck item (WARNING: covers standard click. The
view now reacts to taps rather than clicks);
Double tap -> lets modify a single item name;
Fling (swipe) left/right -> check/uncheck item.
Adds: done (checked) items text is now strikethrough and gray.
Adds: options menu has now an item that clean the current list (deletes
all items marked as done).
Adds: the current list name is now shown in the action bar in the detail
activity.
Adds: detail activity has now the "up" button (that still does nothing).
Bugfix: some accesses to the database are changed because the table
field was wrong (lists table instead of items table) or the WHERE clause
did not include the current opened list.