Better management of settings in ini file

[ilpersi]

This is a follow up to issue #55

Right now the settings are managed using the settings.ini file. This file relies on a custom ini format and it is managed using a custom parser. This parser has few fail-safe checks and if users type in a setting with a wrong format they will likely get an exception.

As a developer I would like to rely on a library like ini4j to manage ini settings. In this way the library would take care of everything and we could focus on features like a launcher.