Improvements: Fix php-fpm path, update base image on build, include APC

Three fixes!  The APC install took way too long to figure out, but it's finally working (the problem was APC can only be enabled through the php-fpm.conf, not php.ini.  If it's enabled in php.ini, nothing works!).

```haskell
    Improve nginx.conf
    
    Workers can be higher and Phabricator complains if we have invalid
    paths in the config.

=======

    Update base image on build
    
    This is so we don't need to fetch new packages every time
    we `run` this Docker container.
    
    We just need to update base packages in this container at build
    time so we don't re-update every run.

=======

    Add APC support
    
    opensuse is stuck on PHP 5.4, so we can't use the PHP 5.5 built
    in opcode cache.  Until we use PHP 5.5 (or base all of this on
    a different system), we can use APC directly here.
    
    At this point, the entire image generates a _clean_ phabricator
    install with no "unresolved setup issues" except for the base
    case of "enable people to create accounts."
```