Image preview plugin to 0.9.X

[totetmatt]

== Transition to 0.9.X == Main work was to make the plugin transition to 0.9.X.

Main issue was the renderImageProcessing (ImageNode.java) function as now the default rendering engine is G2DTarget. It makes the old Processing trick unusable anymore. Therefore, it's now using fully the awt.Graphic2D to render the image on preview and PNG rendering.

No big issue with PDF and SVG rendering.

== UX Changes ==

• Adding a Scaling factor that keep the size aspect but can resize the images only.
• The Default image directory used is your home/Document, if it's changed, the plugin keep the last Directory used even after a restart
• Alpha doesn't have any effect (didn't find correct method with Graphic2D)
• Some error handeling

== To Keep in Mind ==

• Didn't tried on lare graph (Maybe some Reuse of similar images could help ?)

Open to enhancement proposition before merging.

[eduramiba]

Thanks for the pull request! I hope to have some time soon to check all your requests.

[eduramiba]

Merged with improvements, thanks!