[IZPACK-1090] Allow tab completion and password masking in console mode

Post-fixes:
- Really recognize fallback if ConsoleReader cannot be initialized.
On Windows, in some cases it didn't throw an error but initialized an UnsupportedTerminal which made the password field masking not working
- Use System.console() from JDK 1.6 instead of accessing System.in and System.out. Old style left als fallback for unit tests, which can't read System.console().