Add balances widget in sidebar

RT-2463 #inreview
This version does not yet colorize the values when they increase or decrease.
Are you sure you wanna use `max_sig_digits` (maximum significant digits) here?

10.12 will print 10.12
100.12 will print 100.12
1000.12 will print 1000.10
10000.12 will print 10000.00