Allow to specify display to render on for JoglNewtWindow

See the [forum post](http://ardor3d.com/forums/viewtopic.php?f=11&t=274&p=25178#p25176).

This change is fully backwards-compatible. When the connection is not specified (using the existing constructors or passing `null` to the new one) the behavior is exactly the same as before.

Although the code should be fine, I had trouble to use it when a connection string was specified, (e.g. `:99.0`) but I'm quite sure that this is actually a bug in jogl itself:

```
javax.media.opengl.GLException: X11GLXDrawableFactory - Could not initialize shared resources for :99.0
	at jogamp.opengl.x11.glx.X11GLXDrawableFactory$SharedResourceImplementation.createSharedResource(X11GLXDrawableFactory.java:299)
	at jogamp.opengl.SharedResourceRunner.run(SharedResourceRunner.java:269)
	at java.lang.Thread.run(Thread.java:662)
Caused by: java.lang.IllegalArgumentException: Passed thread is original owner: Thread[Thread-1-SharedResourceRunner,5,main]
	at jogamp.common.util.locks.RecursiveThreadGroupLockImpl01Unfairish.addOwner(RecursiveThreadGroupLockImpl01Unfairish.java:163)
	at javax.media.opengl.GLProfile.initProfilesForDeviceCritical(GLProfile.java:1593)
	at javax.media.opengl.GLProfile.initProfilesForDevice(GLProfile.java:1556)
	at javax.media.opengl.GLProfile.getProfileMap(GLProfile.java:1907)
	at javax.media.opengl.GLProfile.get(GLProfile.java:836)
	at jogamp.opengl.x11.glx.X11GLXDrawableFactory$SharedResourceImplementation.createSharedResource(X11GLXDrawableFactory.java:260)
	... 2 more
```

I'm sure that it's a jogl bug because it works if I specify the environment variable `DISPLAY=:99.0` and set `null` as connection string in jogl.

@gouessej If you agree that the code is ok, I would like to merge it anyway to have something to play with.