Unit Representation for different currency values

[utkarshg6]

We want a better method to represent balances.

For example:

- 10,000,000,000 wei can be represented as 10 gwei.
- 10,634,509,800 gwei can be represented as 10.634 Eth
-  123,987,621 wei can be represented as 0.123 gwei

We can use a U256 to store the number in Wei and then divide by billion as many times as it's required to get the unit we need.