- Updated file "build.gradle" to add task "localTest" to support POJO testing.
- added libraries "junit.jar" and "hamcrest-core.jar"
- separated database tables "available_currencies" and "selected_currencies"
- added first POJO test "SelectedCurrenciesDAOTest"
removed "autoincrement" from table "selected_currencies".
Created base adapter "AbstractDbAdapter" containing "SQLiteOpenHelper" and derived adapters for each table in database.
Connected tables "available_currencies" and "selected_currencies" through the currency name.