Add a `user_creatable' property to folder types and make components

use it, so that e.g. you cannot create a folder of type "mailstorage"
or "vtrash".

svn path=/trunk/; revision=11298

shell/Evolution-ShellComponent.idl

@@ -18,6 +18,8 @@ module Evolution {
 		string name;
 		string icon_name;
 
+		boolean user_creatable;
+
 		sequence<string> accepted_dnd_types;
 		sequence<string> exported_dnd_types;
 	};