Improve pgpool-II's installer.

- Move the scripts from pgpool-II's main repository (http://www.pgpool.net).
- A lot of enhances and bug fixes. Created prototypes by Nozomi Anzai, improved them by Yuta Masano.
  - The installer can install the all of pgpool-II's servers and PostgreSQL's servers at once.
  - Remove the restriction that pgpool-II and PostgreSQL are in the same hosts.
  - Recognizes installer.conf which users writes as they like.
  - Add error checks such as that the specified directory already exists, etc.
  - Add paging while executing the script.
  - Separated one too long script into a short main script and some libraries.
Fix typo.
Fix typo.