Optimize the algorithm to calculate the impact value.

[dadiorchen]

Currently, we are just using a simple way to try to get the token package whose impact value equal to the number specified in the transfer request. Hopefully, we can use a better way to do a smarter sum-up algorithm to get the token package.

https://github.com/dadiorchen/treetracker-token-trading-api/tree/impact-value

[sebastiangaertner]

@Kpoke we have the field impact value but have to start using it more. This is currently depending on
1 point for indigenous species
1 point for tree is verified
1 point for grower has been compensated (social impact)