Automatically check for latest lmms version

Make LMMS look for the latest release and inform the user if the package is outdated and no longer supported. This would help the user in trouble shooting and possibly take some load off the issue tracker/support channels.

Add an icon like :warning: with a descriptive text to the **About** window if there is a later release than the one used.

Start by locating the About window implementation and how the running LMMS version is exposed. The work is done when LMMS checks for a later release and shows a warning icon with descriptive text in the About window when the installed version is outdated.

Written by the indexing model from the issue text.