simplify `update_wifi_measure_count` logic by using `on_duplicate`

only give new_wifi points for the first entry and no longer for the first 4
we no longer need the full wifi table in `process_wifi_measure`
only give points for new cells once in `update_cell_measure_count`
add a new UniqueConstraint for the cell table and fill in default values
maintain created field in Wifi table
simplify `update_cell_measure_count` by using `on_duplicate`