Initial shot at support for handling video post-processing in the pipeline

I know this grab is over, but I spent a good chunk of time hammering out a way to perform post-processing of the WARCs that wget-lua generated. Specifically, I added the ability to sample and shrink items that had been marked appropriately (as "bulk" items in the tracker) using FFMPEG. I'm unable to test this against the tracker since it's down --and my adventures in trying (and failing) to get the latest tracker to actually work so that I may test the logic locally are also documented in my gitlog-- but the pipeline does start running.

I figure if nothing else, this work can be used as the starting point for future grabs that need to post process things. If anyone has any comments about my code, please share, no matter how harsh :D It was my first foray into python and I'm sure there are stylistic considerations I missed and "easier" ways to do things that I didn't find with my google-fu. If nothing else, the "SimpleClass" certainly got bloated, and I haven't gotten around to splitting up more of the code into separate def: functions.