This adds the backend code and the buttons that allow deletion of a
wallet.
Formerly you could archive a wallet and thus remove it from view,
at popular request an archived wallet now gets a button in the
wallets overview to delete the actual wallet completely.
This indeed also removes the files from disk, making it unrecoverable.
Additionally, an actually more complex feature, this allows an existing
wallet to have its history removed and start a re-scan to re-download
all transactions and build the balance.
This is useful for debugging or for recovering from buggy code we
probably had in older versions. (nobody is perfect all the time)
tomFlowee
ebf0f38b1f