Protect PHP configuration file 'config.php'

This file (formerly 'Site.conf') is now protected in three ways:
- Renamed to 'config.php', so it won't normally render any output
- Moved to the parent directory, out of the web-accessible area
- Protected with an .htaccess file in that folder:
```
<Files config.php>
	order deny,allow
	deny from all
</Files>
```
The configuration template 'config.php.EXAMPLE' describes the latter two steps
in a comment. Fixes #37.