Auto saving an unsaved project.

NOTE: Added supporte for auto save an unsaved file in case an Erlang or Wings3D crash.

The "temporary" file is saved at preferences folder and is named unsaved.wings. After the unsaved project be saved the file is removed.

Obs: There is many changes, but must of than are tab->to->space changes.
The main changes are in these functions:
wings.erl
 - open_file(none)
 - handle_event({open_file,Name}, St0)
wings_file
 - save_now(Next, #st{file=Name0}=St)
 - autosave(#st{file=undefined} = St)