Added to menu, nearly functions.

The continue button can load the saved game which has the lexically
lowest value name. It can't use the autosaves directory.

TODO:
*FilteredFileNode isn't sorting the children in the saved game directory
by date.
*The autosaves directory isn't checked.
*Translatable strings need to be used, currently the button name's is
the constant: "Continue" and its tooltip is from another button.
*Add translations to the translation files (some already have
translations for this button's tooltip)