URI Cache: Cache pages based files based on the request URI

This class can be used to cache whole pages on files with names based on the request URI.

It takes the current request URI and uses MD5 to compute the name of a file that should store the cached version of the current page.

If the computed cache file does not exist, it starts capturing the output of the current script and stores it in the cache file when the script ends.

If the cache file exists, it reads the cache file contents and outputs it.

The cache file directory and the cached files lifetime are configurable parameters.