move the logic setting GtkSpin port value to setup_for_type()
should fix #11 (closed).
setup_for_type() was forcefully setting the port value with the method default port, potentially overwriting a value coming from a bookmark previously set by init_values()
Instead, let's move the code setting the value to setup_for_type(), defaulting to 0, then to the method port if we've detected a known scheme, and if we're editing a bookmark, take the value from the bookmark.
tested in the following cases:
- creating a new connection -> the port value is set to the scheme default
- editing an existing bookmark -> the value comes from the bookmark
- changing the scheme type on an existing bookmark -> the port value is reset to the scheme default