Mutliple changes for the queue: cronjob, defer indexer, configurations

[TimVroom]

Added the option to let the indexer be offloaded to a queue. Added a cronjob so the queues get processed. Multiple configuration options. More like that...

[lilmuckers]

Woah, i only just saw this pull request!

I like the idea of using a cron to run the workers, as it sidesteps some issues i've found with the shell command to do with database connections. I would probably make it a 5 minute process that ends after a job when the runtime is greater than or equal to 5 minutes. something like:

<?php
//class definition
$runTime = microtime(true);
while(true){
    //get the next job, 
    //run the job

    if((microtime(true) - $runTime) >= 60*5){
        break;
    }
}

As for the index funcitonality - i see what you're doing there, but it sort of belongs in a module on its own that depends on the queue module - see my asyncronous indexing module https://github.com/lilmuckers/magento-lilmuckers_asynchronousindex-enterprise

As such i'm not going to merge this code as-is, this module is purely about adding tools and framework for developers to easily attach workers and queueing systems