* lisp/progmodes/project.el (project-async-shell-command)
(project-shell-command): New commands to run 'async-shell-command'
and 'shell-command' in project's root directory.
(project-prefix-map): Bind commands to '!' and '&'.
* doc/emacs/maintaining.texi (Project File Commands): Document the
new commands.
* etc/NEWS: Announce the new commands.