Add refresh button to chart list
ag_db_save_chart() now sets save_data->db_id after a successful INSERT
ag_window_can_close() now checks for unsaved (db_id == -1) charts, too
ag_window_save_chart() now creates an AgDbSave struct for a new chart

Its db_id is -1, thus considered unsaved.
ag_app_import_chart() now saves the chart immediately after importing
Using g_clear_object() instead of g_object_unref() in ag_window_set_chart
Merge branch 'master' into chart-db