extracted currency helpers to service

...va/de/deadlocker8/budgetmaster/advices/ServiceAdvice.java

...dlocker8/budgetmaster/reports/ReportGeneratorService.java

...de/deadlocker8/budgetmaster/services/CurrencyService.java

.../de/deadlocker8/budgetmaster/services/HelpersService.java

src/main/resources/templates/helpers/navbar.ftl

...resources/templates/transactions/newTransactionMacros.ftl

src/main/resources/templates/transactions/transactions.ftl

...n/resources/templates/transactions/transactionsMacros.ftl