Implementation of the economy API

Located in modules/EconomyAPI with all the same tasks as the root project

*based on v1.0 proposal on genmymodel*

**Changes from original design**
---

**Errors**
  * InvalidAmount stores the amount provided
  * NotEnoughMoney stores the deficit
  * Added InvalidGlobalValue for when globalValue is negative

**Managers**
  * CurrencyManager also has deleteCurrency with no conversion option
  * AccountManager also has purgeCurrency with a conversion option

**Objects**
  * Account also has amounts object (Wasn't in diagram for some reason)
  * Account has setName
  * Account has getAmounts
  * Account has getAmount
  * Currency has setters for name, plural and globalValue

**Tests**
---
  * Creating account
  * Creating 2 currencies
  * Giving ( Valid and invalid )
  * Invalid currency creation ( Negative global value )
  * Taking ( Valid and invalid )
  * Taking too much
  * Purging with convert
  * Purging no convert
  * Deleting account