System Preferences Dialog: provide Option to toggle PDF page numbers generation

[Pitterling]

it would be better if we can choose to insert/not insert the page number into PDF from "Options" -> "System preferences". I tried to add the component, but it seems that "Form Editor" (Netbeans) is needed. Do you handle this?

https://github.com/vlsi/ksar/blob/master/src/main/java/net/atomique/ksar/UI/Preferences.java#L71

see also discussion in PR #61