Move all compression configs under `Compression`

Create subsection under `Compression` to allow users to more
easily mark certain resources as been compressed in order to:

 1) ensure that they are served with the
    `Content-Encoding: gzip` HTTP response header

 2) prevent Apache from recompressing them
    (see: https://github.com/apache/httpd/blob/53823ebd5c93b34995a46ccdad2f84b4f4128cd0/modules/filters/mod_deflate.c#L593-L596)