HGBase Code (Desktop)

Method to extract a color from a RGB value.

Code reorganization.

Extracted method to load an image from an URL.

Method to scale an icon.

Since Java 9 Class.getResource() searches not in the class path but in the package of the class.
So a HGBase class has to be specified to find the images.

Method to add an element to an array.

Add toFloatArray method.

Add method to transform an exception to a string including stack trace.

Add helper method to check if a list is a sublist of another one.

Allow XML node for messages like it is used by Android.