Remove the Edit dialog from the planet stats pane. This goes along with my trend to prefer single windows versus multiple windows for a more
standardized user interface.
Replace Edit and Abandon buttons with a drop-down for type, and text editors for the name and alias.
Remove "Colonize" button, again to reduce the number of separate windows that appear.
Remove some redundant OR statements. Wrapping model data like "#{@data}" is cleaner and gets Gtk's assertions to shut up.
Remove edit_planet_dialog.rb now that it's unnecessary.