[Qt] Pet Peeve: Make File -> Open also know how to open .txn files
[Qt] Pet Peeve: Make File -> Open also know how to open .txn files

- If it's a file ending in .txn, send it to the handler for transaction
files

- Otherwise treat it as a wallet.

This always kind of annoyed me -- I feel lots of users made this UI
mistake of trying to open a .txn with File->Open only to get weird
errors.

fyookball/electrum,fyookball/electrum,fyookball/electrum