Move "up" button from planet stats widget to planet view widget.
Convert hacked table to a real Gtk::Table.
Remove extraneous observe for the planet view container class.
Remove extraneous observe and private methods from system_view_widget and system_view_planet_overview_widget.
Fix two crashes in planet_stats_widget, one related to a race condition, the other because I prematurely removed a function I still needed.
Rework the "Edit Planet" dialog to use Gtk::Table.
Use the "Edit Planet" dialog for both planet view and system view cases.
Delete now-deprecated "Colonize Planet" dialog.