GUI: Settings take immediate effect on the m-editor * main-window.cc (main_window::construct): connect settings change to file-editor * file-editor.h (file-editor::notice_settings): new notice settings method * file-editor.cc (file-editor::notice_settings): new notice settings method and pass-through to all file-editor-tabs * file-editor-tab.h (file-editor::notice_settings): new notice settings method * file-editor-tab.c (file_editor_tab::file_editor_tab): removed all settings to file-editor::notice_settings (file-editor::update_lexer): fix in case settings is 0 (should never happen) (file-editor::notice_settings): all settings moved here