Misc fixes to restore script.

- Fix err function to output to standard err.
- Use err function throughout script to make it more concise.
- Add some more verbosity and examples to the Usage message to make it more
  clear how to use this script.
- Don't output non-error messages to std-err.
- Use -Z option to grep (Is this really necessary?  I'm not sure)
- Start grep pattern with ^ to only match the pattern at the beginning of the
  line