* Adds CustomBuyingPowerModelAlgorithm
This algorithms is an example on how to implement a custom buying power model.
In this particular case, it shows how to override `HasSufficientBuyingPowerForOrder` in order to place orders without sufficient buying power according to the default model.
* Upgrades CustomModelsAlgorithm to Include CustomBuyingPowerModel
The custom buying power model overrides `HasSufficientBuyingPowerForOrderResult` but it doesn't change the trades and, consequently, the regression statistics.
Alexandre Catarino