FormatCoins problem with representations of numbers less than zero

[Miguel Tenorio]

Describe the bug
Currently util.FormatCoins function does not allow representations of numbers that are less than the respective accuracy for that number.

Steps to Reproduce
Steps to reproduce the behavior:

1. Make a transaction of an amount less than zero
2. Run the app
3. Go to a page where you can see the transaction or look for Outputs page
4. See the amount, you should see 0 instead of 0.XXX

Expected behavior
The number should be represented properly, as 0.XXX with all its decimal digits

Possible implementation
Because several accuracy values ​​are powers of 10, we can cleanly divide the number by its accuracy when it is less than the accuracy.