NextReports Designer: Check for updates

Until version 6.2 , NextReports Designer could be checked for new updates using proprietary Install4J process. This allowed the users to see if a new version was available, to download it and to run the installer immediately.

From version 6.2 we want to make the designer to not depend on such proprietary process. Changing this means the designer has to read the last version from an URI and if this version is new compared to the current version, it gives the user a link to the NextReports download page.

Even this is more minimalistic than the existing wizard in previous versions, the benefits will be seen on a long-term NextReports evolution.