Added some initial objects for the new feature of cash exchange
Work in progress: Currency Calculator feature.
[WIP] Currency calculator and exchange rate import.
[WIP] Currency calculator and exchange rate import facility.
[ExchangeRateManagement WIP] Beginn with persistence, added Test, created Tables
[OptionMenu] Kicked out option menu layout files and added OptionSupport
[ExchangeRateManagement WIP] Beginn with persistence implementation (Tables, Daos)
[ExchangeRateManagement WIP] Persistence done without testing
[ExchangeRateManagement WIP] Fixed inital test
[ExchangeRateManagement WIP] Created import db test, restructured tests, added test suite for persistence tests.
[ExchangeRateManagement WIP] Delete exchange rate layout finally done, what a pain.
[ExchangeRateManagement WIP] Finish Exchange Rate Management, UI harmonisation, introduce title labels & remove title text views; Introduce blank texts for participant tab view,  payment tab.
[ExchangeRateManagement WIP] Started on edit and create exchange rate activity.
[ExchangeRateManagement WIP] Finished delete exchange rate activity. Integrate android button clone for popup selection.
[ExchangeRateManagement WIP] Implement last used logic for currency calculator: ExchangeRatePrefsSaveLoadTest added, ExchangeRatePrefsTable amended, add close to DataManager, harmonize test cases in AllExchangeRatePersistenceTestSuite.
[ExchangeRateManagement WIP] Rework currency selection.
[ExchangeRateManagement WIP] Rework currency selection: Hierachical Model. Created CurrencyLastUsedTest.java
Merge branch 'feature/exchange'