Spent addresses balances should not be accounted

[dzhelezov]

To reproduce (on testnet):

• Request funds to a spent address
• Try to spend all the funds

Actual behavior:

• An error is shown (or pending transaction)

Expected behavior:

• Only the balance of unspent addresses is shown
• The balance of spent addresses is still shown in Settings -> Accounts menu
• (Probably needs a separate feature) Add an "EVACUATE" button + warning if the user wants to transfer the funds from the spent address to a new one; that would require migrating all the funds to a new seed (and thus new account)