Autotool the project

Closes issue #6:

  6 - Autotool the project

  https://github.com/ChrisCummins/pat/issues/6

Closes issue #12:

  12 - Make pat multi-user

  This involves separating the shared program files from the per-user
  data, such as:

  /usr/local/bin/pat
  /usr/local/share/pat/pat.py
  /home/bob/.patrc
  /home/bob/pat/cache
  /home/bob/pat/lock

  This feature depends on issue #6 and replaces issue #10.

  https://github.com/ChrisCummins/pat/issues/12