Write algorithms for net worth graphs

[Sovamorco]

Write algorithms for calculating net worth over a historical period of time.

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Imported from trello Members: evanfroe

[Sovamorco]

Imported from trello Original author: evanfroe

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working on the finite calculation for every transaction

[Sovamorco]

Imported from trello Original author: quabey

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@evanfroe this isnt a priority, and we need to set up everything else first