Refactor enhanced installation instructions to INSTALLATION.md #23
Currently, the installation instructions are in README.md. They do not include anything about PHP configuration or Apache. As well, the database section could use some amplification.
This PR implements #21 to enhance and refactor the installation instructions to a new file INSTALLATION.md.
This should be merged after PR #22, as it references new configuration file semantics (config.example.php instead of config.php).