Load default directory from resources if there is no variable specified and relaunch with same arguments for privilege escalation

1. The current version of 4.3 broke the ability to specify default install directories using the TargetDir.os.xxx resource files as described in http://izpack.org/documentation/panels.html#targetpanel.

This fixes the problem by reading in and using the resource files if no TargetDir.os.xxx variable is specifically specified.

2. In addition, in the current version if there is a privilege escalation under Windows, any command line arguments specified are lost when the application is relaunched with a higher privilege.  This was fixed as was calling the correct java executable: javaw.exe for GUI and java.exe for command line.  

I'm not sure why it's showing that the entire TargetPanel.java file changed as there were only 4 lines added.