Add a precision to Assets based on coin

[Rjected]

Is your feature request related to a problem? Please describe.
In many places, we use uint64's to represent values of various coins, which for Bitcoin is generally fine, but for other assets which have higher capacities, this may not be the case.
Also, doing floating point arithmetic with coin values should conform to the specific coin's precision.

Describe the solution you'd like
Figure out how to easily create new Assets (maybe do #15 before this one) with a specified precision for arithmetic, then create said arithmetic methods.

Describe alternatives you've considered
N/A

Additional context
N/A