Fixed #353 - allow selection of "all" accounts

...eadlocker8/budgetmaster/controller/AccountController.java

.../de/deadlocker8/budgetmaster/database/DatabaseParser.java

...eadlocker8/budgetmaster/database/legacy/LegacyParser.java

...in/java/de/deadlocker8/budgetmaster/entities/Account.java

...ava/de/deadlocker8/budgetmaster/entities/AccountType.java

...dlocker8/budgetmaster/repositories/AccountRepository.java

...ker8/budgetmaster/repositories/TransactionRepository.java

.../de/deadlocker8/budgetmaster/services/AccountService.java

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

...deadlocker8/budgetmaster/services/TransactionService.java

src/main/resources/languages/_de.properties

src/main/resources/languages/_en.properties

src/main/resources/static/css/dark/style.css

src/main/resources/static/css/style.css

src/main/resources/static/js/main.js

src/main/resources/templates/accounts/accounts.ftl

src/main/resources/templates/import.ftl

src/main/resources/templates/navbar.ftl

src/main/resources/templates/scripts.ftl

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