Add runscript command with support for scrip fixtures and app scripts

patch and docs for runscripts

We used this script over two months now in internal development and worked very well. one reason for example was, that the complex design of our application didn't work well with static fixtures, in fact it couldn't work by design, many data worked, but some could not. for this we implemented the fixture part. a lot of other maintance work etc and daily cleanups scripts in different modules started to pop up. in a real modular design, every module has to be independend and therefor should implement cleanup scripts init.

Thanks, but no. We've already decided against doing this a few times in the past. Also, with recent Django versions, you can achieve the same thing by writing your own management commands. There's another ticket open to move daily_cleanup and a couple of other utilities into management commands as well.

[In future, please don't promote your own patches to "ready for checkin". That bypasses one layer of triage and review, since the triagers will tend not to look at tickets that are already marked "ready for checkin".]