Add display of savings into user full balance screen

As recently savings balances became available via API, it would be useful to have savings display as part of the user's full balance screen. To make this happen, we can add a checkbox "Savings" into the filtering section, which would allow enabling/displaying the display of the savings. Savings will be displayed based of the token currently selected (HBD or HIVE). In case of VESTS, there are no savings so the filter would be disabled. Savings API is part of the existing API currently used, for more details, check #548 (closed)