gui: configurable synchronization between file browser and octave directory * default-qt-settings: all settings of the file browser are now located in its section, new setting sync_octave_directory * files-dock-widget.cc(constructor): make QToolBar and QAction variables local, add two buttons for syncing from octave to file browser and vice versa, change status-tips into tool-tips * files-dock-widget.cc(set_current_directory): do not emit signal displayed_directory_changed (would change octave dir) * files-dock-widget.cc(do_sync_octave_directory): new function for manually setting the octave dir to the one in the file browser * files-dock-widget.cc(do_sync_browser_directory): new function for manually setting the file browser to the octave directory * files-dock-widget.cc(update_octave_directory): new function called from the main-window when the octave directory has changed * files-doc-widget.cc(display_directory): new second parameter (bool, default is true) determining whether the signal with the new displayed directory should be emitted if synchronizing is enabled * files-dock-widget.cc(notice-settings): read new setting, enalbe or disable the sync buttons and set file browser to octave directory depending on setting * files-dock-widget.h: removed QToolBar and QAction variibles, new varaibles for storing the actual octave directory and whether syncing is desired or not, new functions (do_sync_octave_directory, do_sync_browser_directory, update_octave_directory), function display_directory with second parameter (bool, default true) * libgui/src/icons/ok.png,libgui/src/icons/reload.png: new icons for the toolbar * main-window.cc(change_directory): call new function update_octave_directory instead of display_directory * main-window.cc(construct-window-menu): rename "Current Directory" into "File Browser" * libgui/src/module.mk: new files icons/ok.png and icons/reload.png * settings-dialog.cc(constructor,write_changed_settings): all files-dock-widgets settings in a section, new setting sync_octave_directory * settings-dialog.ui: new setting sync_octave_directory