Edit styles button

[conroy-ricketts]

There should be a button that allows a user to edit the color style of the app. Mainly, to set the color of positive assets which should be green by default, to set the color of negative assets which should be red by default, and to set the color of liabilities which should be red by default on the Account Overview screen. Also, to set the color of positive transactions which should be green by default, to set the color of negative transactions which should be red by default, and to set the color of transfer transactions which should be blue by default on the Transaction History screen.