Make the tool detect if a new version is available and if so, display notice in administration

[mbohal]

To prevent overload, it should be run by cron once a day to get info about the latest version available. If the latest version does not match current version a notice in administration should be shown.

[mbohal]

Is it OK if the releases are newly presented on GitHub instead on http://epartool.download.felis.visionapps.cz?

[DBJRdev]

@mbohal: Yes :)