DRASCULA: Add advanced savegame functionality

This cleans up the save/load code and resolves multiple issues with the
original save/load screen.
Save game timestamps and thumbnails are now implemented, together with
the ability to load a game from the launcher.
F7 is now mapped to the ScummVM load dialog, and F10 to the save dialog
(if the user has selected to use the ScummVM save screen).
NEWS: Mention Drascula save/load changes
TRANSLATION: Add the new translatable files in the drascula engine