algorithm: combine individual intents into estimated order

[ahdinosaur]

job story: when i cast my intent in the context of other individual intents from other members of the group, i should be able to know the current expected order.

the calculation will try to be as close to the desired intents as possible, while also doing best to stay within the given minimum and maximum constraints.

@mischa-saunders and i worked on this in v1, we even wrote tests!

https://github.com/root-systems/cobuy/tree/v1/ordering/util

related to:

• page: individual intent casting #39
• page: group plan (facilitator tweaking) #40
• traffic light order item colors #22

[ahdinosaur]

this is no longer a priority: #137 (comment)