An additional flag `--term-title-format` is introduced to allow the user to control the format of the terminal
title.  It is specified as a python format string, and currently the only variable it will format is `{cwd}`.

An additional flag `--TerminalInteractiveShell.term_title_format` is introduced to allow the user to control the format of the terminal
title.  It is specified as a python format string, and currently the only variable it will format is `{cwd}`.

Fix whatsnew doc for term-title-format feature
Fix whatsnew doc for term-title-format feature
