0.7.24 released

Change the target to Java 8
Use docJGenerator 1.4.4 for the wiki
Move the MDIFileUtils class to the bootstrap package
Add a Configuration2 interface and an AbstractConfiguration2 class to ease the creation of configuration
Move several methods in the AbstractPlugin class to the Plugin interface
Add a initAfterGUI method in the MDIPlugin interface to be called after the applicationGui has been initialized
Breaking change: the setListener method in the PluginsManager has been renamed to setManagerListener