Settings Page / Dialog #47

We should establish a settings page, with the options below (at least initially).

• Preferred fiat Currency (USD, GBP, EUR, etc)

And these options in later stages:

• Select Wallet (multiple accounts)
• Set Alias for selected wallet
• Light/Dark Mode selector
• For Sending: Prefer Privacy vs Exactness
• Subtract transaction fee from amount
  • Normal (Unchecked): 0.01 + TX Fee
  • Subtract from Amount (Checked): 0.01 - TX Fee