LoadFromFile blacklist support

[GoogleCodeExporter]

Consider a site that is static html with a dynamic directory:

  /index.html
  /about.html
  /images/
  /cgi-bin/
  /stylesheets/
  /scripts/
  /subdirA/
  /subdirB/
  /subdirC/
  ...

They would like to set:

  ModPagespeedLoadFromFile "http://www.example.com/" "/var/www/"

But this would break their cgi-bin directory.  While they could add separate 
"ModPagespeedLoadFromFile" directives for every top-level directory except 
cgi-bin, that is awkward, needs to be maintained, doesn't apply to index.html 
or other top-level pages, and may slow mod_pagespeed down.  Finer-grained 
control over LoadFromFile is needed here.

I see two potential solutions, of which I prefer (1):

  1) Add a "ModPagespeedDisableLoadFromFile"
     configuration directive that takes
     priority over ModPagespeedLoadFromFile:

       ModPagespeedLoadFromFile "http://www.example.com/" "/var/www/"
       ModPagespeedDisableLoadFromFile "http://www.example.com/cgi-bin/"

  2) Support directory-level configuration,
     with both a ModPagespeedLoadFromFile and
     a ModPagespeedDisableLoadFromFile.

       <Directory /var/www>
          ModPagespeedLoadFromFile
       </Directory>

       <Directory /var/www/cgi-bin>
          ModPagespeedDisableLoadFromFile
       </Directory>

     In the example of someone with a mostly
     dynamic website that has a /static
     directory you would have:

       <Directory /var/www/static>
          ModPagespeedLoadFromFile
       </Directory>

     (Not loading from file is the default.)

One question is how useful this is: how many sites does it ally to?  While 
traditionally websites were set up this way, dynamic sites may be the default 
now.  Many dynamic sites, however, are actually serving static content that has 
been "baked" in advance.  For example, Movable Type does this by default.

Original issue reported on code.google.com by jefftk@google.com on 11 Jul 2012 at 6:37