aktualizacja polskiego tłumaczenia

:trollface:
clarified some translation comments
just one empty strings file
some random xib updates
update_xibs: ignore xibs w/o strings files
text change: 'to confirm the transaction'
updated credits
auto-select first autocomplete entry

that way you can quickly type something and press enter to select
send: enter in address field moves focus to amount
don't check wallet encryption when disabling backup