gui: provide prefernces for the octave directory at startup * settings-dialog.ui: add check box for restoring previous octave directory and line edit / file dialog for setting startup directory * settings-dialog.cc (constructor): init new input widgets from settings; (write_changed_settings): wirte values from new widgets into settings file; (get_octave_directory): new slot for settings octave dir in a file dialog * main-window.h: new slot handle_octave_ready * main-window.cc (handle_octave_ready): depending on settings set octave directory to the last one from the previous session, the one set in the settings or the current one; (construct): do not set dir here but in handle_octave_ready; (construct_octave_qt_link): pass 'this' to octave link as parent; * octave-interpreter.h: new signal inidication interpreter is initialized * octave-interpreter.cc (constructor): emit new signal after init of interpreter * octave-qt-link.cc (constructor): connect new signal with slot in main window

--- a/libgui/src/octave-interpreter.cc
+++ b/libgui/src/octave-interpreter.cc
@@ -43,6 +43,8 @@
   octave_initialize_interpreter (octave_cmdline_argc, octave_cmdline_argv,
                                  octave_embedded);
 
+  emit octave_ready_signal ();
+
   octave_execute_interpreter ();
 }