Add ineachdir script

Added a script to switch to each directory on stdin (one per line) in turn and run the same command each time.

Also option to print on either stdout or stderr the name of the directory switched into.

For example the following would give the last three commit messages in each of the git repositories listed in the my_list_of_git_repos file:
  cat my_list_of_git_repos | ineachdir -po git log -n 3 | less