* src/gnumeric-util.[ch] (gnumeric_dialog_file_selection): New
function, some code moved from gui-file.c.

* src/workbook.[ch] (workbook_get_filename): New accessor function.

* src/gui-file.h
(gui_file_open): New function.
(gui_file_import): Removed fname argument.

* src/gui-file.c
(gui_file_import): Create and open file selector, using
gnumeric_dialog_file_selection to display it. Use one dialog to select
file and file format, we don't need glade file anymore. Optionally
show all registered openers as importers.
(gui_file_save_as): Uses gnumeric_dialog_file_selection. Take
workbook's current saver if current_saver is NULL (previously we've
been loosing this information), use
gnumeric_option_menu_get_selected_index instead of playing with
signals.
(gui_file_open): New function, some code moved from
dialog_query_load_file.
(gui_file_save): Always call wb_view_preferred_size.
(do_save_as): Take GnumFileSaver as argument.
(cb_select, handle_ok, saver_activate, fill_save_menu,
make_format_chooser, file_dialog_delete_event, fs_key_event,
fs_set_filename): Removed.

* src/workbook-control-gui.c
(cb_file_new): Just call gui_file_open.
(cb_file_import): Call gui_file_import.
(workbook_control_gui_init): Initialize current_saver with NULL.