[Amadeus] Migrate Math cog to Crypto submodule 

We need to migrate the Math cog from Amadeus to Math (as Crypto submodule). 

See the cog [here](https://github.com/Czechbol/Amadeus/blob/master/cogs/math.py).

The cog doesn't use a database and is using the [Mathcrypto](https://mathcrypto.readthedocs.io/en/latest/) library so this will be fairly a easy port.

Feel free to rewrite any part of the cog to make it better/more readable