Implement transaction pool

[ignopeverell]

Keep transactions received from the network. Should occupy only a fixed amount of memory and evict based on time/fees. Eviction should also evict dependent transactions.

[MoaningMyrtle]

Hey there,

Looking to take a crack at this.

Are you pretty happy with the Network/Chain adapter setup in adapters.rs? I was planning on largely duplicating that effort for pool connectivity.

Other than what's in your original post, any potential issues/ implementation thoughts you had?

[ignopeverell]

Sorry, only seeing your comment now.

The higher level adapter approach is working fairly well so far in keeping those components somewhat independent. It's a little early to say if it's a good long term approach but it doesn't seem to create too many problems.

As far as potential issues, the pool needs to be able to iterate easily on all transactions for mining (using some priority selection algorithm) and needs to do some memory accounting for eviction. That's probably the 2 biggest constraints. So I'd design around these first.

[ignopeverell]

Provided by #48.