gtk: add Entry, Scrollbar and Ranges widget
gtk: add Entry, Scrollbar and Ranges widget
gtk: refactor structure of library
gtk: add a couple of -lower interest- widgets
gtk: add convenience widgets which allow to easily create graphical assistants
gtk: add basic dialog widget and derived dialog windows : about, appChooser, fileChooser, message,...
Merge branch 'master' of https://github.com/nheu/nit

Conflicts:
	lib/gtk/gtk.nit
	lib/gtk/gtk_assistant.nit
	lib/gtk/gtk_dialogs.nit
	lib/gtk/gtk_widgets_ext.nit