General code style improvements

A few questions:

• Do we want to keep the using Gtk;? Or do we use the full qualifiers for each type (i.e. Gtk.Box, Dazzle.GraphView)?
• Is it really necessary to mark all classes as public?
• Do we prefer a Java style of construction or a GObject style?
• Do we prefer an explicit this or an implicit this?
• Are the braces mandatory or can they be omitted in the case of an if with a single statement?
• Is it mandatory to always make the access level of each member explicit, or can we keep the private implicit?
• Can we use type inference for everything? In which cases should we make the type explicit?
• Since GLib is imported automatically, can we implicit its namespace (i.e. List instead of GLib.List)?