add possibility for adding dir with subdirectories to load path dialog * files-dock-widget.cc (files_dock_widget): connect new signal for modifying load path to related slot in main window; (contextmenu_add_to_path): do not modify path here anymore, just emit the new signal connected to the new slot in main window; no need to emit signal for modified path here anymore * files-dock-widget.h: remove signal for modified path and add new signal for requesting path modification * main-window.cc (modify_path): new slot moved from files-dock-widget to here, adding or removing dirs to or from the load path with or wihtout subdirs depending on parameters; (handle_set_path_dialog_request): do not connect signal from file browser on changed path any more but connect same signal from main window now, connect signal from path dialog requesting modifying the load path * main-window.h: new signal path_changed_signal indicating a changed path, new slot for modifying the load path * set-path-dialog.cc: include QMenu; (set_path_dialog): add a menu to add dir button and add two new actions to this menu, add without and with subdirs, do not connect button clicked signal because related slots are already provided to the new actions; (add_dir_common): new method adding a dir with or without subdirs to the path depending on boolean parameter; (add_dir): only call common method with false boolean parameter; (add_dir_subdirs): new slot calling call common method with true parameter; * set-path-dialog.h: include ovl.h, new signal modify_path_signal requesting path modification by main window, new method add_dir_common, new slot add_dir_subdirs