Allow log-level to be specified

[ukch]

I've been trying to subclass djangoappengine so that I can pass the dev_appserver_log_level argument to dev_appserver, but it seems impossible with the current setup (currently the only way I can see would be to monkey-patch dev_appserver_main itself, which feels like a Bad Idea.)
Please allow me to specify this value using arguments (--log-level seems like a sensible one).

[aburgel]

Great idea. I'd be happy to take a pull request on this. It should be easy to write.

[ukch]

I actually looked into writing this, but it turns out it's nigh on impossible with the old dev-appserver. I'm happy to branch off the devappserver2 branch and do a PR if you think that's good?

[aburgel]

That sounds good. I want to merge in devappserver2 soon anyways.