Upload support

This pull request introduces upload support. It does not come with documentation, as that will be part of a later pull request. If you wish to test uploading an archive: find any Python package, and run it's setup.py with the sdist argument. It will output a tarball, and you should be able to upload that to Pulp. To verify that it's been uploaded, you should be able to see it in Mongo like this:

```
> db.units_python_package.find()
```

Also, you should find the package you uploaded stored in ```/var/lib/pulp/content/python_package/```.
Ha, I never considered that people might run the tests with translations enabled. As far as I know, we haven't ever translated Pulp. If we did do this and people ran the tests in a different language (can that be done?), I bet there would be several failures. That said, it's easy enough for me to fix this one.