add menu entries to the editor for directly accessing the editor's settings * settings-dialog.ui: tabs with self explaining names * settings-dialog.cc(constructor): name of desired tab as new parameter, open the last or desired tab depending on this parameter; (destructor, write_lexer_settings): update to new tab names * settings-dialog.h: new parameter in constructor * main-window.cc(process_settings_dialog_request): name of desired tab as new parameter, settings-dialog is created with this parameter * main-window.h: new parameter for process_settings_dialog_request * file-editor.cc(request_preferences,request_styles_preferences): new slots emtting a new signal for opening the settings dialog via the main window; (construct): new actions for opening the editor and editor styles settings * file-editor.h: new actions, related slots and signal for main window