attempt to handle java sorting priorities by MC version

settings.getCurrentJava() is used in a lot of places -- still needs some more thought into a more reliable way to do this
ADDED:  java8 error messages

 * Show error message if old pack is started with java 8
 * Java 8 checks can be overridded with command line argument
CHANGED: log link if OSUtils.browse() fails
ADDED: todo for later
Merge pull request #865 from jikuja/java8sorting

Java8sorting
CHANGED: moved authlib status from LaunchFrame to Main
CHANGED: reworked LoadingDialog,

 * use smaller invokeLater()s in mainGUI()
   => smoother startup
CHANGED: minor changes to support splash screen

 * rewrote doneCheckLoad()
 * enable launchButton only if authlib is ready to use
   and launcher installation directory is writeable
CHANGED: minor changes

 * show() LaunchFrame after pack info are loaded
 * minor LoadinDialog message changes