gio-tool: Various fixes related to error messages

This patch contains the following changes:
- Print all errors with "gio: " prefix
- Print file uri in error for each tool allowing multiple locations
- Mark all error messages translatable
- Do not leak strings used in error messages
- Always start error messages with capital letter
- Unify some error messages across various tools
- Fix addional/missing new line characters

https://bugzilla.gnome.org/show_bug.cgi?id=776169

gio/gio-tool-rename.c

@@ -81,7 +81,7 @@ handle_rename (int argc, char *argv[], gboolean do_help)
 
   if (new_file == NULL)
     {
-      g_printerr (_("Error: %s\n"), error->message);
+      print_error (error->message);
       g_error_free (error);
       retval = 1;
     }