[FEATURE] Constant-Product Swap Algorithm (columbus-3)

[nplatias]

Proposed implementation of the swap algorithm described here for columbus-3.
Relevant discussion can be found here.

Attached is my best approximation of sufficiently accurate pseudocode, which ended up being python code : ) It has been written in the spirit of the current market module, and relies on primitives either currently available or easy to implement. The core function is "swap".

A variant of this code is being used for simulations.

Look forward to your input -- @dokwon @YunSuk-Yeo @hanjukim
cp_swaps.zip