Bug fix -  Swing Event Thread does not use JNLP class loader 

## Context
For security reasons, java web start has to be upgraded, to the 1.6.0_51.

All applications using codjo-mad-gui are not working anymore. 
We faces two cases:
* the application menu is not displayed
* a small error window without any title or description is displayed after the login window.

## Description
It's a referenced bug on oracle web site (see http://bugs.sun.com/view_bug.do?bug_id=8017776)

The swing event thread doesn't use the JNLP classloader leading to ```ClassNotFoundExceptions``` when using custom Look and feel.

We fixed the bug by injecting the current classloader in the swing event thread.

NB: As a quick fix, displaying the Java console fixes the problem.